ZIP Code
Overview
ZIP codes are a system of postal code
Postal code
A postal code is a series of letters and/or digits appended to a postal address for the purpose of sorting mail. Once postal codes were introduced, other applications became possible.In February 2005, 117 of the 190 member countries of the Universal Postal Union had postal code systems...

s used by the United States Postal Service
United States Postal Service
The United States Postal Service is an independent agency of the United States government responsible for providing postal service in the United States...

 (USPS) since 1963. The term ZIP, an acronym for Zone Improvement Plan, is properly written in capital letters and was chosen to suggest that the mail
Mail
Mail, or post, is a system for transporting letters and other tangible objects: written documents, typically enclosed in envelopes, and also small packages are delivered to destinations around the world. Anything sent through the postal system is called mail or post.In principle, a postal service...

 travels more efficiently, and therefore more quickly, when senders use the code in the postal address
Address (geography)
An address is a collection of information, presented in a mostly fixed format, used for describing the location of a building, apartment, or other structure or a plot of land, generally using political boundaries and street names as references, along with other identifiers such as house or...

. The basic format consists of five decimal numerical digit
Numerical digit
A digit is a symbol used in combinations to represent numbers in positional numeral systems. The name "digit" comes from the fact that the 10 digits of the hands correspond to the 10 symbols of the common base 10 number system, i.e...

s. An extended ZIP+4 code, introduced in the 1980s, includes the five digits of the ZIP code, a hyphen
Hyphen
The hyphen is a punctuation mark used to join words and to separate syllables of a single word. The use of hyphens is called hyphenation. The hyphen should not be confused with dashes , which are longer and have different uses, or with the minus sign which is also longer...

, and four more digits that determine a more precise location than the ZIP code alone.
Encyclopedia
ZIP codes are a system of postal code
Postal code
A postal code is a series of letters and/or digits appended to a postal address for the purpose of sorting mail. Once postal codes were introduced, other applications became possible.In February 2005, 117 of the 190 member countries of the Universal Postal Union had postal code systems...

s used by the United States Postal Service
United States Postal Service
The United States Postal Service is an independent agency of the United States government responsible for providing postal service in the United States...

 (USPS) since 1963. The term ZIP, an acronym for Zone Improvement Plan, is properly written in capital letters and was chosen to suggest that the mail
Mail
Mail, or post, is a system for transporting letters and other tangible objects: written documents, typically enclosed in envelopes, and also small packages are delivered to destinations around the world. Anything sent through the postal system is called mail or post.In principle, a postal service...

 travels more efficiently, and therefore more quickly, when senders use the code in the postal address
Address (geography)
An address is a collection of information, presented in a mostly fixed format, used for describing the location of a building, apartment, or other structure or a plot of land, generally using political boundaries and street names as references, along with other identifiers such as house or...

. The basic format consists of five decimal numerical digit
Numerical digit
A digit is a symbol used in combinations to represent numbers in positional numeral systems. The name "digit" comes from the fact that the 10 digits of the hands correspond to the 10 symbols of the common base 10 number system, i.e...

s. An extended ZIP+4 code, introduced in the 1980s, includes the five digits of the ZIP code, a hyphen
Hyphen
The hyphen is a punctuation mark used to join words and to separate syllables of a single word. The use of hyphens is called hyphenation. The hyphen should not be confused with dashes , which are longer and have different uses, or with the minus sign which is also longer...

, and four more digits that determine a more precise location than the ZIP code alone. The term ZIP code was originally registered as a servicemark (a type of trademark
Trademark
A trademark, trade mark, or trade-mark is a distinctive sign or indicator used by an individual, business organization, or other legal entity to identify that the products or services to consumers with which the trademark appears originate from a unique source, and to distinguish its products or...

) by the U.S. Postal Service, but its registration has since expired.

Background

The United States Post Office Department
United States Post Office Department
The Post Office Department was the name of the United States Postal Service when it was a Cabinet department. It was headed by the Postmaster General....

 (USPOD) implemented postal zones for large cities in 1943. For example:
Mr. John Smith
3256 Epiphenomenal Avenue
Minneapolis 16, Minnesota.


The "16" was the number of the postal zone within the city.

By the early 1960s a more general system was needed, and on July 1, 1963, non-mandatory ZIP codes were announced for the whole country. Simultaneously with the introduction of the ZIP code, two-letter state abbreviations were introduced. These were to be written with both letters capitalized. The reason for the two-letter abbreviations is that it was thought that a long city name coupled with a multi-letter state abbreviation (e.g. Mass. for Massachusetts) would be too long for address labels used on magazines when the ZIP code was added. Robert Moon
Robert Moon (postal inspector)
Robert Aurand Moon , sometimes called "Mr. ZIP", is considered the father of the ZIP Code or Zone Improvement Plan, a mechanism to route mail in the United States...

, an employee of the post office, is considered the father of the ZIP code; he submitted his proposal in 1944 while working as a postal inspector
United States Postal Inspection Service
The United States Postal Inspection Service is the law enforcement arm of the United States Postal Service. Its jurisdiction is defined as "crimes that may adversely affect or fraudulently use the U.S...

.
The post office gives credit to Moon for only the first three digits of the ZIP code, which describe the sectional center facility (SCF) or "sec center." An SCF is a central mail processing facility with those three digits. The SCF sorts mail to all post offices with those first three digits in their ZIP codes. The mail is sorted according to the final two digits of the ZIP code and sent to the corresponding post offices in the early morning. Sectional centers do not deliver mail and are not open to the public (though the building may include a post office open to the public), and most of the workers are employed to work night shift
Shift work
Shift work is an employment practice designed to make use of the 24 hours of the clock. The term "shift work" includes both long-term night shifts and work schedules in which employees change or rotate shifts....

. Mail picked up at post offices is sent to their own SCF in the afternoon, where the mail is sorted overnight. In the cases of large cities, the last two digits coincided with the older postal zone number, thus:
Mr. John Smith
3256 Epiphenomenal Avenue
Minneapolis, Minnesota 55416


In 1967, these were made mandatory for second- and third-class bulk mail
Bulk mail
Bulk mail broadly refers to mail that is mailed and processed in bulk at reduced rates. The term does not denote any particular purpose for the mail; but in general usage is synonymous with "junk mail."...

ers, and the system was soon adopted generally. The United States Post Office used a cartoon character, whom it called Mr. ZIP
Mr. ZIP
Mr. ZIP, informally "Zippy", is a cartoon character used in the 1960s by the United States Post Office Department, and in the 1970s by its successor, the United States Postal Service, to encourage the general public to include the ZIP code in all mailings....

, to promote use of the ZIP code. He was often depicted with a legend such as "USE ZIP CODE" in the selvage
Selvage
The selvage or selvedge is the term for the self-finished edges of fabric. The selvages keep the fabric from unraveling or fraying. The selvages are a result of how the fabric is created...

 of panes of stamp
Postage stamp
A postage stamp is a small piece of paper that is purchased and displayed on an item of mail as evidence of payment of postage. Typically, stamps are made from special paper, with a national designation and denomination on the face, and a gum adhesive on the reverse side...

s or on labels contained in, or the covers of, booklet panes of stamps.

ZIP+4

In 1983, the U.S. Postal Service began using an expanded ZIP code system that it called ZIP+4, often called "plus-four codes", "add-on codes", or "add ons".

A ZIP+4 code uses the basic five-digit code plus four additional digits to identify a geographic segment within the five-digit delivery area, such as a city block
City block
A city block, urban block or simply block is a central element of urban planning and urban design. A city block is the smallest area that is surrounded by streets. City blocks are the space for buildings within the street pattern of a city, they form the basic unit of a city's urban fabric...

, a group of apartments, an individual high-volume receiver of mail or any other unit that could use an extra identifier to aid in efficient mail sorting and delivery. But initial attempts to promote universal use of the new format met with public resistance, and today the plus-four code is not required. In general, mail is read by a multiline optical character reader
Multiline Optical Character Reader
A Multiline Optical Character Reader, or MLOCR, is a type of mail sorting machine that uses Optical Character Recognition technology to determine how to route mail through the postal system....

 (MLOCR) that almost instantly determines the correct ZIP+4 code from the address and—along with the even more specific delivery point
Delivery point
In a postal system, a delivery point is a single mailbox or other place at which mail is delivered. It differs from a street address, in that each address may in fact have several delivery points, such as an apartment flat, office department, or other room...

—sprays a Postnet
POSTNET
POSTNET is a barcode symbology that was used by the United States Postal Service to assist in directing mail. The ZIP Code or ZIP+4 code is encoded in half- and full-height bars...

 barcode on the face of the mailpiece that corresponds to 11 digits—nine for the ZIP+4 code and two for the delivery point.

For post-office box
Post Office box
A post-office box or Post Office box is a uniquely addressable lockable box located on the premises of a post office station....

es, the general (but not invariable) rule is that each box has its own ZIP+4 code. The add-on code is often one of the following: the last four digits of the box number (e.g., PO Box 58001, Washington DC 20037-8001), zero plus the last three digits of the box number (e.g., PO Box 12344, Chicago IL 60612-0344), or, if the box number consists of fewer than four digits, enough zeros prepended to the front of the box number to produce a four-digit number (e.g., PO Box 52, Ambler PA 19002-0052). However, there is no uniform rule, so the ZIP+4 code must be looked up individually for each box.

It is common to use add-on code 9998 for mail addressed to the postmaster (to which requests for pictorial cancellations are usually addressed), 9999 for general delivery
Poste restante
Poste restante or general delivery is a service where the post office holds mail until the recipient calls for it...

 and other high-numbered add-on codes for business reply mail
Freepost
Freepost is a postal service provided by various postal administrations, whereby a person sends mail without affixing postage, and the recipient pays the postage when collecting the mail...

. For a unique ZIP code (explained below), the add-on code is typically 0001.

Postal bar code

The ZIP code is often translated into a barcode
Barcode
A barcode is an optical machine-readable representation of data, which shows data about the object to which it attaches. Originally barcodes represented data by varying the widths and spacings of parallel lines, and may be referred to as linear or 1 dimensional . Later they evolved into rectangles,...

 called Postnet
POSTNET
POSTNET is a barcode symbology that was used by the United States Postal Service to assist in directing mail. The ZIP Code or ZIP+4 code is encoded in half- and full-height bars...

 that is printed on the mailpiece to make it easier for automated machines to sort. Unlike most barcode symbologies, Postnet uses long and short bars, not thin and thick bars. The barcode can be printed by the person who sends the mail (some word-processing programs such as WordPerfect
WordPerfect
WordPerfect is a word processing application, now owned by Corel.Bruce Bastian, a Brigham Young University graduate student, and BYU computer science professor Dr. Alan Ashton joined forces to design a word processing system for the city of Orem's Data General Corp. minicomputer system in 1979...

 and Microsoft Word
Microsoft Word
Microsoft Word is a word processor designed by Microsoft. It was first released in 1983 under the name Multi-Tool Word for Xenix systems. Subsequent versions were later written for several other platforms including IBM PCs running DOS , the Apple Macintosh , the AT&T Unix PC , Atari ST , SCO UNIX,...

 include the feature), or the post office will put one on when it processes the piece. In general, the post office uses OCR
Optical character recognition
Optical character recognition, usually abbreviated to OCR, is the mechanical or electronic translation of scanned images of handwritten, typewritten or printed text into machine-encoded text. It is widely used to convert books and documents into electronic files, to computerize a record-keeping...

 technology, though a human may have to read the address if absolutely necessary.

People who send bulk mail
Bulk mail
Bulk mail broadly refers to mail that is mailed and processed in bulk at reduced rates. The term does not denote any particular purpose for the mail; but in general usage is synonymous with "junk mail."...

 can get a discount
Discounts and allowances
Discounts and allowances are reductions to a basic price of goods or services.They can occur anywhere in the distribution channel, modifying either the manufacturer's list price , the retail price , or the list price Discounts and allowances are reductions to a basic price of goods or services.They...

 on postage if they have printed the barcode themselves. This requires more than just a simple font
Typeface
In typography, a typeface is the artistic representation or interpretation of characters; it is the way the type looks. Each type is designed and there are thousands of different typefaces in existence, with new ones being developed constantly....

; mailing list
Mailing list
A mailing list is a collection of names and addresses used by an individual or an organization to send material to multiple recipients. The term is often extended to include the people subscribed to such a list, so the group of subscribers is referred to as "the mailing list", or simply "the...

s must be standardized with up-to-date Coding Accuracy Support System (CASS)-certified software that adds and verifies a full, correct ZIP+4 code and an additional two digit
Numerical digit
A digit is a symbol used in combinations to represent numbers in positional numeral systems. The name "digit" comes from the fact that the 10 digits of the hands correspond to the 10 symbols of the common base 10 number system, i.e...

s representing the exact delivery point
Delivery point
In a postal system, a delivery point is a single mailbox or other place at which mail is delivered. It differs from a street address, in that each address may in fact have several delivery points, such as an apartment flat, office department, or other room...

. Furthermore, mail must be sorted in a specific scheme and be accompanied by documentation verifying this. These steps are usually done with PAVE-certified software that also prints the barcoded address labels and barcoded sack or tray tags.

This means that every single mailable point in the country has its own 12-digit number (at least in theory). The delivery-point digits (the 10th and 11th digits) are calculated based on the primary or secondary number of the address. The USPS publishes the rules for calculating the delivery point in a document called the CASS Technical Guide. The last digit is always a check digit
Check digit
A check digit is a form of redundancy check used for error detection, the decimal equivalent of a binary checksum. It consists of a single digit computed from the other digits in the message....

, which is obtained by summing all 5, 9 or 11 digits, taking the residue
Modular arithmetic
In mathematics, modular arithmetic is a system of arithmetic for integers, where numbers "wrap around" after they reach a certain value—the modulus....

 modulo 10 of this sum (i.e., the remainder after dividing by 10) and finally subtracting this from 10. (Thus, the check digit for 10001-0001 00 would be 7, since 1+1+1=3, 3≡3(mod 10) and 10–3=7.) An application needs only to print something like /100010001007/ in the 12-point
Point (typography)
In typography, a point is the smallest unit of measure, being a subdivision of the larger pica. It is commonly abbreviated as pt. The point has long been the usual unit for measuring font size and leading and other minute items on a printed page....

 Postnet font to create a valid barcode. The slashes "/" are translated into start/stop characters (one long bar), and each digit is translated into a sequence of two long bars and three short bars
Two-out-of-five code
In telecommunication, a two-out-of-five code is an m of n code that provides exactly ten possible combinations, and thus is popular for representing decimal digits using five bits...

.

On business-reply mail, the FIM
Facing Identification Mark
The Facing Identification Mark, or FIM, is a bar code designed by the United States Postal Service to assist in the automated processing of mail. The FIM is a set of vertical bars printed on the envelope or postcard near the upper edge, just to the left of the postage area...

 code primarily indicates the orientation (facing) of the mailpiece, since there is, in general, not a stamp
Postage stamp
A postage stamp is a small piece of paper that is purchased and displayed on an item of mail as evidence of payment of postage. Typically, stamps are made from special paper, with a national designation and denomination on the face, and a gum adhesive on the reverse side...

 or postage meter
Postage meter
A postage meter is a mechanical device used to create and apply physical evidence of postage to mailed matter. Postage meters are regulated by a country's postal authority; for example, in the United States, the United States Postal Service specifies the rules for the creation, support, and use...

 imprint containing fluorescent ink (which is usually used by the facing machine to orient mail). Additionally, FIM codes A and C indicate that a Postnet bar code is present, allowing this mail to bypass the MOCR
Multiline Optical Character Reader
A Multiline Optical Character Reader, or MLOCR, is a type of mail sorting machine that uses Optical Character Recognition technology to determine how to route mail through the postal system....

 and go straight to a barcode scanning machine. For that reason, even though courtesy reply mail
Courtesy reply mail
Courtesy reply mail, or CRM, is a type of mail in which a business sends pre-printed, self-addressed envelopes or postcards to customers, who then affix postage stamps to the envelopes or postcards and mail them back to the business...

 and metered reply mail
Metered reply mail
Metered reply mail, or MRM, is a type of mail in which a business sends pre-printed, self-addressed envelopes or postcards to customers, with postage prepaid on the envelopes or postcards with a postage meter...

 are mailed with a stamp or a postage-meter imprint, they typically carry an FIM code, namely FIM A, to indicate that the Postnet bar code is present. The FIM D barcode is used for computer-generated
Computer-generated
The term computer-generated most often refers to a sound or visual that has been created in whole or in part with the aid of computer software...

 indicia from online postage meters.

By type/use

There are four types of ZIP codes: Unique (assigned to a single high-volume address), P.O.-box-only (used only for P.O. boxes at a given facility, not for any other type of delivery), Military (used to route mail for the U.S. military) and Standard (all other ZIP codes). As examples of Unique ZIP codes, certain governmental agencies, universities, businesses or buildings that receive extremely high volumes of mail
Mail
Mail, or post, is a system for transporting letters and other tangible objects: written documents, typically enclosed in envelopes, and also small packages are delivered to destinations around the world. Anything sent through the postal system is called mail or post.In principle, a postal service...

 have their own ZIP codes, such as 20505 for the Central Intelligence Agency
Central Intelligence Agency
The Central Intelligence Agency is a civilian intelligence agency of the United States government. It is an executive agency and reports directly to the Director of National Intelligence, responsible for providing national security intelligence assessment to senior United States policymakers...

 in Washington, D.C.
Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....

, 81009 for the Federal Citizen Information Center
Federal Citizen Information Center
The Federal Citizen Information Center , originally the Federal Consumer Information Center, is a department in the United States government's General Services Administration...

 of the U.S. General Services Administration (GSA) in Pueblo, Colorado
Pueblo, Colorado
Pueblo is a Home Rule Municipality that is the county seat and the most populous city of Pueblo County, Colorado, United States. The population was 106,595 in 2010 census, making it the 246th most populous city in the United States....

; 30385 for BellSouth
BellSouth
BellSouth Corporation is an American telecommunications holding company based in Atlanta, Georgia. BellSouth was one of the seven original Regional Bell Operating Companies after the U.S...

 in Atlanta; and 21412 for Bancroft Hall
Bancroft Hall
Bancroft Hall at the United States Naval Academy in Annapolis, Maryland, is the largest single dormitory in the world. Bancroft Hall, named after former Secretary of the Navy George Bancroft, is home for the entire brigade of 4,000 midshipmen, and contains some 1,700 rooms, of corridors, and of...

, the midshipman dormitory at the United States Naval Academy
United States Naval Academy
The United States Naval Academy is a four-year coeducational federal service academy located in Annapolis, Maryland, United States...

.
An example of a P.O.-box-only ZIP code is 22313, which is used for P.O. boxes at the main post office in Alexandria, Virginia
Alexandria, Virginia
Alexandria is an independent city in the Commonwealth of Virginia. As of 2009, the city had a total population of 139,966. Located along the Western bank of the Potomac River, Alexandria is approximately six miles south of downtown Washington, D.C.Like the rest of northern Virginia, as well as...

, as well as for the United States Patent and Trademark Office
United States Patent and Trademark Office
The United States Patent and Trademark Office is an agency in the United States Department of Commerce that issues patents to inventors and businesses for their inventions, and trademark registration for product and intellectual property identification.The USPTO is based in Alexandria, Virginia,...

. In the area surrounding that post office, home and business mail delivery addresses use ZIP code 22314, which is thus a Standard ZIP code.

Primary State Prefixes

ZIP codes are numbered with the first digit representing a certain group of U.S. state
U.S. state
A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

s, the second and third digits together representing a region
Region
Region is most commonly found as a term used in terrestrial and astrophysics sciences also an area, notably among the different sub-disciplines of geography, studied by regional geographers. Regions consist of subregions that contain clusters of like areas that are distinctive by their uniformity...

 in that group (or perhaps a large city) and the fourth and fifth digits representing a group of delivery addresses within that region. The main town in a region (if applicable) often gets the first ZIP codes for that region; afterward, the numerical order often follows the alphabetical order. Because ZIP codes are intended for efficient postal delivery, there are unusual cases where a ZIP code crosses state boundaries, such as a military facility spanning multiple states or remote areas of one state most easily serviced from an adjacent state. For example ZIP code 42223 spans Christian KY and Montgomery TN, and ZIP code 97635 spans Lake OR and Modoc CA.

In general, the first three digits designate a sectional center facility
Sectional center facility (SCF)
A Destination Sectional Center Facility is a Processing and Distribution Center of the United States Postal Service that serves a designated geographical area defined by one or more three-digit ZIP Code prefixes....

, the mail sorting and distribution center for an area. A sectional center facility may have more than one three-digit code assigned to it. For example, the Northern Virginia sectional center facility in Merrifield is assigned codes 220, 221, 222 and 223. In some cases, a sectional center facility may serve an area in an adjacent state, usually due to the lack of an appropriate location for a center in that region. For example, 739 in Oklahoma
Oklahoma
Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...

 is assigned to Liberal, Kansas
Liberal, Kansas
Liberal is the county seat of Seward County, Kansas, United States. As of the 2010 census, the city population was 20,525.- History :S.S. Rogers built the first house in what would become Liberal in 1872. Rogers became famous in the region for giving water to weary travelers...

; 865 in Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

 is assigned to Gallup, New Mexico
Gallup, New Mexico
- Demographics :As of the census of 2000, there were 20,209 people, 6,810 households, and 4,869 families residing in the city. The population density was 1,513.7 people per square mile...

; and 961 in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 to Reno, Nevada
Reno, Nevada
Reno is the county seat of Washoe County, Nevada, United States. The city has a population of about 220,500 and is the most populous Nevada city outside of the Las Vegas metropolitan area...

.

In terms of geographic location, many of the lowest ZIP codes, which begin with '0', are in the New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...

 region. Also in the '0' region are New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...

 (non-contiguous with the remainder of the '0' area), Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...

, the U.S. Virgin Islands and APO/FPO military addresses for personnel stationed in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, Southwest Asia
Southwest Asia
Western Asia, West Asia, Southwest Asia or Southwestern Asia are terms that describe the westernmost portion of Asia. The terms are partly coterminous with the Middle East, which describes a geographical position in relation to Western Europe rather than its location within Asia...

 and aboard vessels based in the waters adjoining those lands; APO/FPO addresses are also used by U.S. diplomatic and consulary facilities. The lowest ZIP code is in Holtsville, New York
Holtsville, New York
Holtsville is a hamlet in Suffolk County, New York, United States. The population was 17,006 at the 2000 census....

 (00501, a ZIP code exclusively for the U.S. Internal Revenue Service center there). Other low ZIP codes are 00601 for Adjuntas, Puerto Rico
Adjuntas, Puerto Rico
Adjuntas is a small mountainside municipality in Puerto Rico located central midwest of the island on the Central Mountain range , north of Yauco, Guayanilla and Peñuelas; southeast of Utuado; east of Lares and Yauco; and west of Ponce. Adjuntas is spread over 16 wards and Adjuntas Pueblo...

; 01001 for Agawam, Massachusetts
Agawam, Massachusetts
The Town of Agawam is a city in Hampden County, Massachusetts, United States. The population was 28,438 at the 2010 census. Agawam sits on the western side of the Connecticut River, directly across from the City of Springfield, Massachusetts...

, and 01002 for Amherst, Massachusetts
Amherst, Massachusetts
Amherst is a town in Hampshire County, Massachusetts, United States in the Connecticut River valley. As of the 2010 census, the population was 37,819, making it the largest community in Hampshire County . The town is home to Amherst College, Hampshire College, and the University of Massachusetts...

. Until 2001, there were six ZIP codes lower than 00501 that were numbered from 00210 to 00215 (located in Portsmouth, New Hampshire
Portsmouth, New Hampshire
Portsmouth is a city in Rockingham County, New Hampshire in the United States. It is the largest city but only the fourth-largest community in the county, with a population of 21,233 at the 2010 census...

) and were used by the Diversity Immigrant Visa
Diversity Immigrant Visa
The Diversity Immigrant Visa program is a United States congressionally mandated lottery program for receiving a United States Permanent Resident Card. It is also known as the Green Card Lottery. The lottery is administered on an annual basis by the Department of State and conducted under the terms...

 program to receive applications from non-U.S. citizens.

The numbers increase southward along the East Coast, such as 02115 (Boston
Boston
Boston is the capital of and largest city in Massachusetts, and is one of the oldest cities in the United States. The largest city in New England, Boston is regarded as the unofficial "Capital of New England" for its economic and cultural impact on the entire New England region. The city proper had...

), 10001 (New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

), 19103 (Philadelphia), 20008 (Washington, D.C.
Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....

), 30303 (Atlanta) and 33130 (Miami
Miami, Florida
Miami is a city located on the Atlantic coast in southeastern Florida and the county seat of Miami-Dade County, the most populous county in Florida and the eighth-most populous county in the United States with a population of 2,500,625...

) (these are only examples, as each of these cities contain several ZIP codes in the same range). From there, the numbers increase heading westward and northward east of the Mississippi River, southward west of the Mississippi River, and northward on the west coast. For example, 40202 is in Louisville
Louisville, Kentucky
Louisville is the largest city in the U.S. state of Kentucky, and the county seat of Jefferson County. Since 2003, the city's borders have been coterminous with those of the county because of a city-county merger. The city's population at the 2010 census was 741,096...

, 50309 in Des Moines, 60601 in Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...

, 77063 in Houston, 80202 in Denver
Denver, Colorado
The City and County of Denver is the capital and the most populous city of the U.S. state of Colorado. Denver is a consolidated city-county, located in the South Platte River Valley on the western edge of the High Plains just east of the Front Range of the Rocky Mountains...

, 94111 in San Francisco
San Francisco, California
San Francisco , officially the City and County of San Francisco, is the financial, cultural, and transportation center of the San Francisco Bay Area, a region of 7.15 million people which includes San Jose and Oakland...

, 98101 in Seattle
Seattle, Washington
Seattle is the county seat of King County, Washington. With 608,660 residents as of the 2010 Census, Seattle is the largest city in the Northwestern United States. The Seattle metropolitan area of about 3.4 million inhabitants is the 15th largest metropolitan area in the country...

, and 99950 in Ketchikan, Alaska
Ketchikan, Alaska
Ketchikan is a city in Ketchikan Gateway Borough, Alaska, United States, the southeasternmost sizable city in that state. With an estimated population of 7,368 in 2010 within the city limits, it is the fifth most populous city in the state....

 (the highest ZIP code).

The first digit of the ZIP code is allocated as follows:
  • 0 = Connecticut
    Connecticut
    Connecticut is a state in the New England region of the northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, and the state of New York to the west and the south .Connecticut is named for the Connecticut River, the major U.S. river that approximately...

     (CT), Massachusetts
    Massachusetts
    The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...

     (MA), Maine
    Maine
    Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost...

     (ME), New Hampshire
    New Hampshire
    New Hampshire is a state in the New England region of the northeastern United States of America. The state was named after the southern English county of Hampshire. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Atlantic Ocean to the east, and the Canadian...

     (NH), New Jersey
    New Jersey
    New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...

     (NJ), Puerto Rico
    Puerto Rico
    Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...

     (PR), Rhode Island
    Rhode Island
    The state of Rhode Island and Providence Plantations, more commonly referred to as Rhode Island , is a state in the New England region of the United States. It is the smallest U.S. state by area...

     (RI), Vermont
    Vermont
    Vermont is a state in the New England region of the northeastern United States of America. The state ranks 43rd in land area, , and 45th in total area. Its population according to the 2010 census, 630,337, is the second smallest in the country, larger only than Wyoming. It is the only New England...

     (VT), Virgin Islands
    Virgin Islands
    The Virgin Islands are the western island group of the Leeward Islands, which are the northern part of the Lesser Antilles, which form the border between the Caribbean Sea and the Atlantic Ocean...

     (VI), Army Post Office Europe (AE), Fleet Post Office Europe (AE)
  • 1 = Delaware
    Delaware
    Delaware is a U.S. state located on the Atlantic Coast in the Mid-Atlantic region of the United States. It is bordered to the south and west by Maryland, and to the north by Pennsylvania...

     (DE), New York
    New York
    New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

     (NY), Pennsylvania
    Pennsylvania
    The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...

     (PA)
  • 2 = District of Columbia (DC), Maryland
    Maryland
    Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...

     (MD), North Carolina
    North Carolina
    North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...

     (NC), South Carolina
    South Carolina
    South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...

     (SC), Virginia
    Virginia
    The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...

     (VA), West Virginia
    West Virginia
    West Virginia is a state in the Appalachian and Southeastern regions of the United States, bordered by Virginia to the southeast, Kentucky to the southwest, Ohio to the northwest, Pennsylvania to the northeast and Maryland to the east...

     (WV)
  • 3 = Alabama
    Alabama
    Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...

     (AL), Florida
    Florida
    Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

     (FL), Georgia
    Georgia (U.S. state)
    Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...

     (GA), Mississippi
    Mississippi
    Mississippi is a U.S. state located in the Southern United States. Jackson is the state capital and largest city. The name of the state derives from the Mississippi River, which flows along its western boundary, whose name comes from the Ojibwe word misi-ziibi...

     (MS), Tennessee
    Tennessee
    Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...

     (TN), Army Post Office Americas (AA), Fleet Post Office Americas (AA)
  • 4 = Indiana
    Indiana
    Indiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...

     (IN), Kentucky
    Kentucky
    The Commonwealth of Kentucky is a state located in the East Central United States of America. As classified by the United States Census Bureau, Kentucky is a Southern state, more specifically in the East South Central region. Kentucky is one of four U.S. states constituted as a commonwealth...

     (KY), Michigan
    Michigan
    Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....

     (MI), Ohio
    Ohio
    Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...

     (OH)
  • 5 = Iowa
    Iowa
    Iowa is a state located in the Midwestern United States, an area often referred to as the "American Heartland". It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of the French colony of New...

     (IA), Minnesota
    Minnesota
    Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...

     (MN), Montana
    Montana
    Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

     (MT), North Dakota
    North Dakota
    North Dakota is a state located in the Midwestern region of the United States of America, along the Canadian border. The state is bordered by Canada to the north, Minnesota to the east, South Dakota to the south and Montana to the west. North Dakota is the 19th-largest state by area in the U.S....

     (ND), South Dakota
    South Dakota
    South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...

     (SD), Wisconsin
    Wisconsin
    Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...

     (WI)
  • 6 = Illinois
    Illinois
    Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...

     (IL), Kansas
    Kansas
    Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...

     (KS), Missouri
    Missouri
    Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...

     (MO), Nebraska
    Nebraska
    Nebraska is a state on the Great Plains of the Midwestern United States. The state's capital is Lincoln and its largest city is Omaha, on the Missouri River....

     (NE)
  • 7 = Arkansas
    Arkansas
    Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...

     (AR), Louisiana
    Louisiana
    Louisiana is a state located in the southern region of the United States of America. Its capital is Baton Rouge and largest city is New Orleans. Louisiana is the only state in the U.S. with political subdivisions termed parishes, which are local governments equivalent to counties...

     (LA), Oklahoma
    Oklahoma
    Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...

     (OK), Texas
    Texas
    Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...

     (TX)
  • 8 = Arizona
    Arizona
    Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

     (AZ), Colorado
    Colorado
    Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

     (CO), Idaho
    Idaho
    Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....

     (ID), New Mexico
    New Mexico
    New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...

     (NM), Nevada
    Nevada
    Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...

     (NV), Utah
    Utah
    Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...

     (UT), Wyoming
    Wyoming
    Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...

     (WY)
  • 9 = Alaska
    Alaska
    Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

     (AK), American Samoa
    American Samoa
    American Samoa is an unincorporated territory of the United States located in the South Pacific Ocean, southeast of the sovereign state of Samoa...

     (AS), California
    California
    California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

     (CA), Guam
    Guam
    Guam is an organized, unincorporated territory of the United States located in the western Pacific Ocean. It is one of five U.S. territories with an established civilian government. Guam is listed as one of 16 Non-Self-Governing Territories by the Special Committee on Decolonization of the United...

     (GU), Hawaii
    Hawaii
    Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

     (HI), Marshall Islands
    Marshall Islands
    The Republic of the Marshall Islands , , is a Micronesian nation of atolls and islands in the middle of the Pacific Ocean, just west of the International Date Line and just north of the Equator. As of July 2011 the population was 67,182...

     (MH), Federated States of Micronesia
    Federated States of Micronesia
    The Federated States of Micronesia or FSM is an independent, sovereign island nation, made up of four states from west to east: Yap, Chuuk, Pohnpei and Kosrae. It comprises approximately 607 islands with c...

     (FM), Northern Mariana Islands
    Northern Mariana Islands
    The Northern Mariana Islands, officially the Commonwealth of the Northern Mariana Islands , is a commonwealth in political union with the United States, occupying a strategic region of the western Pacific Ocean. It consists of 15 islands about three-quarters of the way from Hawaii to the Philippines...

     (MP), Oregon
    Oregon
    Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...

     (OR), Palau
    Palau
    Palau , officially the Republic of Palau , is an island nation in the Pacific Ocean, east of the Philippines and south of Tokyo. In 1978, after three decades as being part of the United Nations trusteeship, Palau chose independence instead of becoming part of the Federated States of Micronesia, a...

     (PW), Washington (WA), Army Post Office Pacific (AP), Fleet Post Office Pacific (AP)

Secondary Regional Prefixes (123xx) and Local ZIP Codes (12345)

The next two digits represent the sectional center facility (e.g. 477xx = Vanderburgh County, Indiana
Vanderburgh County, Indiana
As of the census of 2000, there were 171,922 people, 70,623 households, and 44,421 families residing in the county. The population density was 733 people per square mile . There were 76,300 housing units at an average density of 325 per square mile...

), and the fourth and fifth digits represent the area of the city (if in a metropolitan area
Metropolitan area
The term metropolitan area refers to a region consisting of a densely populated urban core and its less-populated surrounding territories, sharing industry, infrastructure, and housing. A metropolitan area usually encompasses multiple jurisdictions and municipalities: neighborhoods, townships,...

), or a village/town (outside metro areas): 47722 (4=Indiana, 77=Vanderburgh County, 22=University of Evansville
University of Evansville
The University of Evansville is a small, private university with approximately 3,050 students located in Evansville, Indiana. Founded in 1854 as Moores Hill College, it is located near the interchange of the Lloyd Expressway and U.S. Route 41. It is affiliated with the United Methodist Church...

 area). When a sectional center facility's area crosses state lines, that facility is assigned separate three-digit prefixes for the states that it serves.

In most urban areas, like 462 for Marion County, Indiana
Marion County, Indiana
Marion County is a county located in the U.S. state of Indiana. Census 2010 recorded a population of 903,393, making it the largest county in the state and 55th most populated county in the country, greater than the population of six states. The county seat is Indianapolis, the state capital and...

, the three-digit prefix will often exist in one county, while, in rural and most suburban areas, the prefix will exist in multiple counties, for example, the neighboring 476 prefix is found in part or in entirely in six counties: Gibson, Pike, Posey, Spencer, Vanderburgh, and Warrick. In some cases, an urban county may have more than one prefix. This is the case with Allen (467, 468), Lake (464, 463), St. Joseph (465, 466), and Vanderburgh (476, 477) Counties. Cities like Chicago, Houston, Los Angeles and New York have multiple prefixes within their city limits.

Despite the geographic derivation of most ZIP codes, the codes themselves do not represent geographic regions; in general, they correspond to address groups or delivery routes. As a consequence, ZIP code "areas" can overlap, be subsets of each other, or be artificial constructs with no geographic area (such as 095 for mail to the Navy, which is not geographically fixed). In similar fashion, in areas without regular postal routes (rural route
Rural delivery service
Rural delivery service refers to the delivery of mail in what are traditionally considered rural areas. In the United States, rural letter carriers began service with the experiments with Rural Free Delivery in 1891...

 areas) or no mail delivery (undeveloped areas), ZIP codes are not assigned or are based on sparse delivery routes, and hence the boundary between ZIP code areas is undefined. For example, some residents in or near Haubstadt, Indiana
Haubstadt, Indiana
Haubstadt is a town in Johnson Township, Gibson County, Indiana, United States. The population was 1,529 at the 2000 census.-Geography:Haubstadt is located at ....

, which has the zip code 47639, have mailing addresses with 47648, the ZIP code for neighboring Fort Branch, Indiana
Fort Branch, Indiana
Fort Branch is the largest town and second largest community in Gibson County, Indiana, United States after Princeton. The population was 2,320 at the 2000 census.-Geography:Fort Branch is located at ....

, while others living in or near Fort Branch have addresses with 47639. Many rural counties have similar logistical inconsistencies caused by the aforementioned sparse delivery routes, often known as Rural Routes or by some other similar designation.

For example, almost all U.S. government agencies in and around the capital are assigned ZIP codes starting with 20200 to 20599, which are Washington, D.C. ZIP codes, even if they are not located in Washington itself. While the White House
White House
The White House is the official residence and principal workplace of the president of the United States. Located at 1600 Pennsylvania Avenue NW in Washington, D.C., the house was designed by Irish-born James Hoban, and built between 1792 and 1800 of white-painted Aquia sandstone in the Neoclassical...

 itself is located in ZIP code 20006, it has the ZIP code 20500. The Nuclear Regulatory Commission
Nuclear Regulatory Commission
The Nuclear Regulatory Commission is an independent agency of the United States government that was established by the Energy Reorganization Act of 1974 from the United States Atomic Energy Commission, and was first opened January 19, 1975...

 is located in Rockville, Maryland
Rockville, Maryland
Rockville is the county seat of Montgomery County, Maryland, United States. It is a major incorporated city in the central part of Montgomery County and forms part of the Baltimore-Washington Metropolitan Area. The 2010 U.S...

, at ZIP code 20852, but has been assigned by the Postal Service the address "Washington, DC 20555".

In similar manner, the ZIP code for the Metropolitan Washington Airports Authority
Metropolitan Washington Airports Authority
Metropolitan Washington Airports Authority is an independent airport authority, created by the Commonwealth of Virginia and the District of Columbia with the consent of the United States Congress to oversee management, operations, and capital development of Washington, D.C.'s two major airports:...

, a federally-chartered independent authority, is 20001-6000, even though the physical address of the Authority's office, "1 Aviation Circle", is in Arlington, Virginia.

One current exception to this rule is the United States Patent and Trademark Office
United States Patent and Trademark Office
The United States Patent and Trademark Office is an agency in the United States Department of Commerce that issues patents to inventors and businesses for their inventions, and trademark registration for product and intellectual property identification.The USPTO is based in Alexandria, Virginia,...

. When the USPTO was located in the Arlington, Virginia
Arlington County, Virginia
Arlington County is a county in the Commonwealth of Virginia. The land that became Arlington was originally donated by Virginia to the United States government to form part of the new federal capital district. On February 27, 1801, the United States Congress organized the area as a subdivision of...

 neighborhood of Crystal City, it was assigned by the Postal Service the address "Washington, DC 20231" despite being physically located in ZIP code 22202. However, the USPTO now uses a ZIP code (22313-1450 in ZIP+4) assigned to its current physical location in Alexandria, Virginia
Alexandria, Virginia
Alexandria is an independent city in the Commonwealth of Virginia. As of 2009, the city had a total population of 139,966. Located along the Western bank of the Potomac River, Alexandria is approximately six miles south of downtown Washington, D.C.Like the rest of northern Virginia, as well as...

.

In rare circumstances, a locality is assigned a ZIP code that does not match the rest of the state; in other words, a ZIP code may cross state lines. In general, the locality is so isolated that it is most conveniently served from a sectional center in another state. Examples:
  • Fishers Island
    Fishers Island
    Fishers Island, approximately 9 miles long and 1 mile wide, is located at the eastern end of Long Island Sound, 2 miles off the southeastern coast of Connecticut across Fishers Island Sound...

    , New York, bears the ZIP code 06390 and is served from Connecticut — all other New York ZIP codes (excepting those at Holtsville
    Holtsville, New York
    Holtsville is a hamlet in Suffolk County, New York, United States. The population was 17,006 at the 2000 census....

     for the IRS
    Internal Revenue Service
    The Internal Revenue Service is the revenue service of the United States federal government. The agency is a bureau of the Department of the Treasury, and is under the immediate direction of the Commissioner of Internal Revenue...

    ) begin with "1".
  • Some Texas ZIP codes are served from New Mexico (most notably some El Paso
    El Paso, Texas
    El Paso, is a city in and the county seat of El Paso County, Texas, United States, and lies in far West Texas. In the 2010 census, the city had a population of 649,121. It is the sixth largest city in Texas and the 19th largest city in the United States...

     ZIP codes) and thus bear codes beginning with "885" (contiguous numerically with 870-884 NM) rather than "799".
  • Returned government parcels from the District of Columbia are sent to ZIP codes beginning with "569", so that returned parcels are security checked at a remote facility (this was put into place after the 2001 anthrax attacks
    2001 anthrax attacks
    The 2001 anthrax attacks in the United States, also known as Amerithrax from its Federal Bureau of Investigation case name, occurred over the course of several weeks beginning on Tuesday, September 18, 2001, one week after the September 11 attacks. Letters containing anthrax spores were mailed to...

    ).
  • Some Arkansas roads north of Bull Shoals Lake
    Bull Shoals Lake
    Bull Shoals Lake is an artificial lake or reservoir in the Ozark Mountains of northern Arkansas and southern Missouri. It has hundreds of miles of lake arms and coves perfect for boating, water sports, swimming, and fishing...

     can best be accessed by the Protem, Missouri
    Protem, Missouri
    Protem is an unincorporated community in southeastern Taney County, Missouri, United States, about ten miles north of the Arkansas state line. It is located on Route 125. A fire station, a post office, and some homes are located there. The community was founded in 1870...

    , delivery unit (ZIP code 65733).
  • Fort Campbell
    Fort Campbell
    Fort Campbell is a United States Army installation located astraddle the Kentucky-Tennessee border between Hopkinsville, Kentucky, and Clarksville, Tennessee...

     (ZIP code 42223), primarily in Kentucky, main entrance is in Tennessee.
  • Cincinnati/Northern Kentucky International Airport
    Cincinnati/Northern Kentucky International Airport
    Cincinnati/Northern Kentucky International Airport , sometimes called the Greater Cincinnati Airport is located in Hebron, unincorporated Boone County, Kentucky, United States and serves the Greater Cincinnati metropolitan area. Despite being located in Boone County, the airport operations are...

    , despite being located across the Ohio River
    Ohio River
    The Ohio River is the largest tributary, by volume, of the Mississippi River. At the confluence, the Ohio is even bigger than the Mississippi and, thus, is hydrologically the main stream of the whole river system, including the Allegheny River further upstream...

     from Cincinnati in Hebron, Kentucky
    Hebron, Kentucky
    Hebron is an unincorporated community in Boone County, Kentucky, United States. It is the location of Cincinnati/Northern Kentucky International Airport, which serves Cincinnati and the tri-state area.- Growth :...

    , uses ZIP code 45275 for mailing only, due to the fact the Kenton County
    Kenton County, Kentucky
    Kenton County is a county located in the Commonwealth of Kentucky, United States. It was formed in 1840. In 2010, the population was 159,720. It is the third most populous county in Kentucky behind Jefferson County and Fayette County. Its county seats are Covington and Independence...

     Airport Board, which owns and operates the airport, maintains a P.O. Box physically located at the main post office in Cincinnati. The physical address of the airport is 2939 Terminal Drive, Hebron, Kentucky, 41048. In essence the mail for the Kenton County Airport Board has an Ohio
    Ohio
    Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...

     ZIP code but the physical address of the airport is a Kentucky
    Kentucky
    The Commonwealth of Kentucky is a state located in the East Central United States of America. As classified by the United States Census Bureau, Kentucky is a Southern state, more specifically in the East South Central region. Kentucky is one of four U.S. states constituted as a commonwealth...

     ZIP code.

ZIP codes and previous zoning lines

A ZIP code's address and the city name written on the same line do not necessarily mean that address is within that city. The Postal Service designates one default place name for each ZIP code. This may be an actual incorporated town or city, a subentity of a large city or an unincorporated census-designated place
Census-designated place
A census-designated place is a concentration of population identified by the United States Census Bureau for statistical purposes. CDPs are delineated for each decennial census as the statistical counterparts of incorporated places such as cities, towns and villages...

. Additional place names may be recognized as acceptable for a certain ZIP code. Still others are deemed not acceptable, and if used may result in a delay in mail delivery.

Default place names are typically the actual city or town that the address is located in. However, for many cities that have incorporated since ZIP codes were introduced, the actual city name is not the default place name. Many databases automatically assign the default place name for a ZIP code, without regard to any acceptable place names. For example, Centennial, Colorado
Centennial, Colorado
The city of Centennial is a Home Rule City located in Arapahoe County, Colorado, United States, and part of the Denver-Aurora metropolitan area. The city was to have a total population of 100,377 in 2010 census. Centennial is the tenth-most populous municipality in the state of Colorado and its...

 is divided among seven ZIP codes assigned to Aurora
Aurora, Colorado
City of Aurora is a Home Rule Municipality spanning Arapahoe, Adams, and Douglas counties in Colorado. Aurora is an eastern suburb of the Denver-Aurora-Broomfield, CO Metropolitan Statistical Area . The city is the third most populous city in the Colorado and the 56th most populous city in the...

, Englewood
Englewood, Colorado
The city of Englewood is a Home Rule Municipality located in Arapahoe County, Colorado, United States. As of 2007, the city is estimated to have a total population of 32,532. Englewood is part of the Denver-Aurora Metropolitan Area. Englewood is located in the South Platte River Valley east of the...

 or Littleton
Littleton, Colorado
Littleton is a Home Rule Municipality contained in Arapahoe, Douglas, and Jefferson counties in the U.S. state of Colorado. Littleton is a suburb of the Denver-Aurora Metropolitan Statistical Area. Littleton is the county seat of Arapahoe County and the 20th most populous city in the state of...

 as its default place names. Thus, from the perspective of the U.S. Postal Service, the city of Centennial does not exist—it is part of Aurora, Englewood or Littleton. In the ZIP-code directory, Centennial addresses are listed under those three cities. And since it is acceptable to write "Centennial" in conjunction with any of the seven ZIP codes, one can write "Centennial" in an address that is actually in Aurora, Englewood, or Littleton, as long as it is in one of the shared ZIP codes.

Acceptable place names are usually added to a ZIP code in cases where the ZIP-code boundaries divide them between two or more cities, as in the case of Centennial. However, in many cases only the default name can be used, even when many addresses in the ZIP code are in another city. People sometimes must use the name of a post office rather than their own city.

For example, approximately 85% of the area served by the ZIP code 85254, to which the place name Scottsdale, Arizona
Scottsdale, Arizona
Scottsdale is a city in the eastern part of Maricopa County, Arizona, United States, adjacent to Phoenix. According to the U.S. Census Bureau, as of 2010 the population of the city was 217,385...

, is assigned, is actually inside the city limits of neighboring Phoenix
Phoenix, Arizona
Phoenix is the capital, and largest city, of the U.S. state of Arizona, as well as the sixth most populated city in the United States. Phoenix is home to 1,445,632 people according to the official 2010 U.S. Census Bureau data...

. This is because the Scottsdale post office serves this area. This may lead some residents of the ZIP code to mistakenly believe they live in Scottsdale when they actually live in Phoenix.

Similarly, Missouri City, Texas
Missouri City, Texas
Missouri City is a city located in the U.S. state of Texas within the metropolitan area. The city is mostly in Fort Bend County with a small portion within Harris County. As of the 2000 U.S...

, straddles Harris
Harris County, Texas
As of the 2010 Census, the population of the county was 4,092,459, White Americans made up 56.6% of Harris County's population; non-Hispanic whites represented 33.0% of the population. Black Americans made up 18.9% of the population. Native Americans made up 0.7% of Harris County's population...

 and Fort Bend
Fort Bend County, Texas
Fort Bend County is a county located along the Gulf Coast region in the U.S. state of Texas within the Houston–Sugar Land–Baytown metropolitan area. In 2000 its population was 354,452, while the 2010 U.S...

 counties. The portion within Harris County is within the ZIP code 77071, which must use the city name of Houston instead of Missouri City. At the same time, a small portion of the city of Houston is in Fort Bend County in the ZIP code 77489, and residents there must use the name Missouri City for their address even though they are in Houston.

This also occurs in some rural areas where portions of one town have their mail delivered by other post offices. For example, while most of the town of Plainfield, Massachusetts
Plainfield, Massachusetts
Plainfield is a town on the northwestern edge of Hampshire County, Massachusetts, United States, about 25 miles east of Pittsfield and 30 miles northwest of Northampton. The population was 589 at the 2000 census...

 is in zip code 01070, some sections of town are in the zip code area for the neighboring town of Cummington
Cummington, Massachusetts
Cummington is a town in Hampshire County, Massachusetts, United States. The population was 978 at the 2000 census. It is part of the Springfield, Massachusetts Metropolitan Statistical Area.- History :...

 with zip code 01026. Only the default name of Cummington
Cummington, Massachusetts
Cummington is a town in Hampshire County, Massachusetts, United States. The population was 978 at the 2000 census. It is part of the Springfield, Massachusetts Metropolitan Statistical Area.- History :...

 is allowed in zip code 01026, so residents of parts of Plainfield
Plainfield, Massachusetts
Plainfield is a town on the northwestern edge of Hampshire County, Massachusetts, United States, about 25 miles east of Pittsfield and 30 miles northwest of Northampton. The population was 589 at the 2000 census...

 must list their address as being in Cummington
Cummington, Massachusetts
Cummington is a town in Hampshire County, Massachusetts, United States. The population was 978 at the 2000 census. It is part of the Springfield, Massachusetts Metropolitan Statistical Area.- History :...

.

These phenomena are repeated across the country. The previously mentioned Englewood, Colorado
Englewood, Colorado
The city of Englewood is a Home Rule Municipality located in Arapahoe County, Colorado, United States. As of 2007, the city is estimated to have a total population of 32,532. Englewood is part of the Denver-Aurora Metropolitan Area. Englewood is located in the South Platte River Valley east of the...

 is an inner-ring suburb that was built out by the 1960s. Its post office served the area that is now the high-growth southern tier of the Denver metropolitan area
Denver-Aurora Metropolitan Area
The Denver-Aurora-Broomfield, CO Metropolitan Statistical Area is a United States Census Bureau defined Metropolitan Statistical Area in the State of Colorado that includes the City and County of Denver and nine suburban counties. The Census Bureau estimates that the population was 2,357,404 on...

, and ZIP codes in this area were assigned Englewood as their default place name. A business community as large as downtown Denver has grown in this area, with headquarters for many internationally recognized corporations. These companies indicate Englewood as their location (the default postal place name), although they are actually located in other cities. As a result, there are really two Englewoods — the actual city, small and with a largely working-class
Working class
Working class is a term used in the social sciences and in ordinary conversation to describe those employed in lower tier jobs , often extending to those in unemployment or otherwise possessing below-average incomes...

 residential population, and, a number of miles away, the postal Englewood, a vast suburban area of upscale subdivisions and office parks that have nothing to do with the city of Englewood yet share a split identity with it solely because of ZIP codes. People who say they live or work in Englewood and identify closely with it may rarely enter the actual city. In Indiana
Indiana
Indiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...

, the ZIP code for a town usually indicates the ZIP code for its corresponding township, as nearly all of Indiana's small town post offices have rural routes.

Acceptable place names also come into play in areas where citizens identify more strongly with a particular urban center
Urban Center
The Urban Center is a gallery on Madison Avenue in New York City , which is run by the Municipal Art Society . The gallery serves to champion the fields of urban planning and design in New York, and is also the site of MAS' community development workshops, seminars, lectures, and other educational...

 than their own municipality. For example, Allegheny County, Pennsylvania
Allegheny County, Pennsylvania
Allegheny County is a county in the southwestern part of the U.S. state of Pennsylvania. As of the 2010 census, the population was 1,223,348; making it the second most populous county in Pennsylvania, following Philadelphia County. The county seat is Pittsburgh...

, has 130 distinct municipalities, yet many of the county's residents, and even some residents of adjacent counties, commonly use Pittsburgh, PA as their postal address. Similarly, Hollywood, CA is an acceptable place name for ZIP code 90028, despite the fact that Hollywood is a district of Los Angeles and not a municipality or census-designated area (the default place name is Los Angeles, CA
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...

).

Many ZIP codes are for village
Village
A village is a clustered human settlement or community, larger than a hamlet with the population ranging from a few hundred to a few thousand , Though often located in rural areas, the term urban village is also applied to certain urban neighbourhoods, such as the West Village in Manhattan, New...

s, census-designated place
Census-designated place
A census-designated place is a concentration of population identified by the United States Census Bureau for statistical purposes. CDPs are delineated for each decennial census as the statistical counterparts of incorporated places such as cities, towns and villages...

s, portions of cities, or other entities that are not municipalities. For example, ZIP code 03750 is for Etna, New Hampshire
Etna, New Hampshire
Etna, originally named "Mill Village," is a small village within the town of Hanover, New Hampshire, in the United States. It is located in southwestern Grafton County, approximately east of Hanover's downtown and south of the village of Hanover Center, on Mink Brook...

, but Etna is not a city or town; it is actually a village district in the town of Hanover
Hanover, New Hampshire
Hanover is a town along the Connecticut River in Grafton County, New Hampshire, United States. The population was 11,260 at the 2010 census. CNN and Money magazine rated Hanover the sixth best place to live in America in 2011, and the second best in 2007....

, which itself is assigned the ZIP code 03755. Another example is ZIP code 08043, which corresponds to the census-designated place of Kirkwood, New Jersey
Kirkwood, New Jersey
Kirkwood is an unincorporated area within Voorhees Township in Camden County, New Jersey, United States. Together with Voorhees and Kirkwood Voorhees, the area is served as United States Postal Service ZIP Code 08043....

, but actually serves the entirety of Voorhees Township
Voorhees Township, New Jersey
-Demographics:As of the census of 2000, there were 28,126 people, 10,489 households, and 7,069 families residing in the township. The population density was 2,424.0 people per square mile . There were 11,084 housing units at an average density of 955.2 per square mile...

. This is also the case in LaGrange, New York
LaGrange, New York
LaGrange is a town in Dutchess County, New York, United States. The population was 14,928 at the 2000 census. The town was named after the ancestral estate of the Marquis de Lafayette.-History:...

, a portion of which is served by the 12603 ZIP code based in the neighboring town of Poughkeepsie
Poughkeepsie (town), New York
Poughkeepsie is a town in Dutchess County, New York, United States. The population was 42,777 at the 2000 census. The name is derived from the native term, "Uppu-qui-ipis-in," which means "reed-covered hut by the water."...

. The rest of LaGrange is served by the LaGrangeville Post Office. LaGrangeville is itself not a town at all, but a section of LaGrange. Willow Grove, Pennsylvania
Willow Grove, Pennsylvania
Willow Grove is a census-designated place in Montgomery County, Pennsylvania. A community in Philadelphia's northern suburbs, the population was 15,726 at the 2010 census. It is located in Abington Township and Upper Moreland Township...

, served by the 19090 ZIP code, is a village that straddles the border of Upper Moreland Township
Upper Moreland Township, Pennsylvania
Upper Moreland Township is a township in Montgomery County, Pennsylvania, United States. The population was 24,015 at the 2010 census. Upper Moreland Township is primarily a residential community with distinctive neighborhoods that are complemented by several thriving business, industrial, and...

 and Abington Township
Abington Township, Montgomery County, Pennsylvania
Abington Township is a township in Montgomery County, Pennsylvania, United States. The population was 55,310 in as of the 2010 census.Abington Township is one of Montgomery County's oldest communities dating back to before 1700 and being incorporated in 1704. It is home to some of the county's...

, and that post office also serves a small portion of Upper Dublin Township
Upper Dublin Township, Pennsylvania
Upper Dublin Township is a township in Montgomery County, Pennsylvania, United States. The population was 25,569 at the 2010 census.Upper Dublin is made up of several community areas, many of which are unincorporated areas in Montgomery County with no legal status, and are used primarily by the US...

. Furthermore, non-municipal place names may also share ZIP codes with municipal place names. For example, West Windsor Township, New Jersey
West Windsor Township, New Jersey
-Demographics:As of Census 2010, West Windsor had a population of 27,165. The median age was 39.6. The racial and ethnic composition of the population was 54.9% White, 3.7% Black or African American, 0.1% Native American, 37.7% Asian, 1.0% some other race and 2.6% reporting two or more races...

, is commonly referred to in most mailing databases as Princeton Junction
Princeton Junction, New Jersey
Princeton Junction is also a New Jersey Transit and Amtrak station on the Northeast Corridor line.Princeton Junction is a census-designated place and unincorporated area located within West Windsor Township, in Mercer County, New Jersey...

, a census-designated place within West Windsor.

Postal designations for place names become de facto locations for their addresses, and as a result it is difficult to convince residents and businesses that they actually are located in another city or town different from the "default" place name associated with their ZIP codes. Because of issues of confusion and lack of identity, some cities, such as Signal Hill, California
Signal Hill, California
Signal Hill is a small city in California located in the Greater Los Angeles area. Signal Hill, completely surrounded by the city of Long Beach, was incorporated on April 22, 1924, roughly three years after oil was discovered in Signal Hill. As of the 2010 census, the city population was...

, have successfully petitioned the Postal Service to change ZIP-code boundaries or create new ZIP codes so their cities become the default place name for addresses within the ZIP code.

Postal designation confusion may have financial implications for local governments, because mail volume is one factor used by the U.S. Census Bureau to estimate population changes between decennial census enumerations. Sometimes local officials in a community that is not the default place name for a ZIP code but is an acceptable place name will advise residents to always use the name of the community, because if the census estimate of that town's population is low they may receive less funds that are computed based on population. A typical example is Paddock Lake, Wisconsin
Paddock Lake, Wisconsin
Paddock Lake is a village in Kenosha County, Wisconsin, United States. The population was 3,012 at the 2000 census.-Education:Paddock Lake is the home of the regional high school, Westosha Central High School.-Geography:...

, whose default place name is Salem
Salem, Kenosha County, Wisconsin
Salem is a town in Kenosha County, Wisconsin, United States. The population was 9,871 at the 2000 census. The unincorporated communities of Benet Lake, Salem, Salem Oaks, Trevor, Voltz Lake, and Wilmot are located in the town...

. Paddock Lake is incorporated as a village within the town of Salem, even though there are more people in the village of Paddock Lake than there are in the unincorporated parts of the town of Salem. Further confusion is caused because Silver Lake, Wisconsin
Silver Lake, Wisconsin
Silver Lake is a village in Kenosha County, Wisconsin, United States. The population was 2,341 at the 2000 census.-Geography:Silver Lake is located at ....

, which is also a village in the town of Salem and is of similar size and status to Paddock Lake, has its own ZIP code and post office.

In another case, the U.S. Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...

 (FCC) denied a radio station
Radio station
Radio broadcasting is a one-way wireless transmission over radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both...

 (now WNNX
WNNX (FM)
WWWQ FM 99.7, known as "Q100", is an Atlanta radio station airing a top-40 contemporary hit radio format. It is owned and operated by Cumulus Media from the same building as its other co-owned sister stations WNNX FM "Rock 100.5", W258BU FM 99.1 "99X", and W250BC FM 97.9 "Journey 97-9"...

 FM) a move requiring a change in its city of license
City of license
A city of license or community of license, in American and Canadian broadcasting, is the community that a radio station or television station is officially licensed to serve by that country's broadcast regulator....

 to Sandy Springs
Sandy Springs, Georgia
Sandy Springs is a city in north Georgia, United States. It is a northern suburb of Atlanta. With a 2010 population of 93,853, Sandy Springs is the sixth-largest city in the state and the second-largest city in Metro Atlanta. Sandy Springs is located in north Fulton County, Georgia, just south of...

, Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...

, largely because it was not a city (until municipal incorporation in late 2005), despite being the seventh-largest place in the state by population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...

. The FCC cited the use of "Atlanta" on letters of support from local organizations, even though the USPS forced them to use Atlanta for 30328 until well after incorporation took effect. Currently "Sandy Springs" is only "acceptable", despite none of 30328 being in Atlanta, or anywhere else outside the Sandy Springs city limit. This even applies to the ZIP code used only for PO boxes at the Sandy Springs main post office.

Because ZIP codes and their associated place names can ignore county lines, problems may occur where street addresses are based on quadrant location within a county. For example, 30339 spans over Vinings, Georgia
Vinings, Georgia
Vinings is a census-designated place and an unincorporated town in Cobb County, Georgia, just across the Chattahoochee River from Atlanta. As of the 2010 census, the town had a total population of 9,734. It is located between the affluent West Paces Ferry section of Buckhead in northwest Atlanta,...

 and Atlanta, Georgia
Atlanta, Georgia
Atlanta is the capital and most populous city in the U.S. state of Georgia. According to the 2010 census, Atlanta's population is 420,003. Atlanta is the cultural and economic center of the Atlanta metropolitan area, which is home to 5,268,860 people and is the ninth largest metropolitan area in...

, in southeastern Cobb County
Cobb County, Georgia
Cobb County is a county located in the U.S. state of Georgia. Its county seat and largest city is Marietta, which is located in the center of the county. The county was named for Thomas Willis Cobb, who in the early 19th century was a United States representative and senator from Georgia...

; therefore every street address is labeled SE, and has a house number on that county's grid (according to the distance from the town square
Town square
A town square is an open public space commonly found in the heart of a traditional town used for community gatherings. Other names for town square are civic center, city square, urban square, market square, public square, and town green.Most town squares are hardscapes suitable for open markets,...

 in the county seat
County seat
A county seat is an administrative center, or seat of government, for a county or civil parish. The term is primarily used in the United States....

). However, because the USPS demands the use of Atlanta, Vinings addresses are written such that they appear to be in southeast Atlanta, instead of on the opposite (northwest metro Atlanta
Metro Atlanta
The Atlanta metropolitan area or metro Atlanta, officially designated by the US Census Bureau as the Atlanta-Sandy Springs-Marietta Metropolitan Statistical Area, is the most populous metro area in the U.S. state of Georgia and the ninth-largest metropolitan statistical area in the United States...

) side where they actually are.

Division and reallocation of ZIP codes

Like area codes, ZIP codes are sometimes divided and changed, especially when a rural
Rural
Rural areas or the country or countryside are areas that are not urbanized, though when large areas are described, country towns and smaller cities will be included. They have a low population density, and typically much of the land is devoted to agriculture...

 area becomes suburb
Suburb
The word suburb mostly refers to a residential area, either existing as part of a city or as a separate residential community within commuting distance of a city . Some suburbs have a degree of administrative autonomy, and most have lower population density than inner city neighborhoods...

an. Typically, the new codes become effective once announced, and a grace period (e.g., one year) is provided in which the new and old codes are used concurrently so that postal patrons in the affected area can notify correspondents, order new stationery, etc.

In rapidly growing communities, it is sometimes necessary to open a new sectional center facility, which must then be allocated its own three-digit ZIP-code prefix or prefixes. Such allocation can be done in various ways. For example, when a new sectional center facility was opened at Dulles Airport
Washington Dulles International Airport
Washington Dulles International Airport is a public airport in Dulles, Virginia, 26 miles west of downtown Washington, D.C. The airport serves the Baltimore-Washington-Northern Virginia metropolitan area centered on the District of Columbia. It is named after John Foster Dulles, Secretary of...

 in Virginia, the prefix 201 was allocated to that facility; therefore, for all post offices to be served by that sectional center facility the ZIP code changed from an old code beginning with 220 or 221 to a new code or codes beginning with 201. However, when a new sectional center facility was opened to serve Montgomery County, Maryland
Montgomery County, Maryland
Montgomery County is a county in the U.S. state of Maryland, situated just to the north of Washington, D.C., and southwest of the city of Baltimore. It is one of the most affluent counties in the United States, and has the highest percentage of residents over 25 years of age who hold post-graduate...

, no new prefix was assigned. Instead, ZIP codes in the 207 and 208 ranges, which had previously been assigned alphabetically, were reshuffled so that 207xx ZIP codes in the county were changed to 208xx codes, while 208xx codes outside that county were changed to 207xx codes. Because Silver Spring
Silver Spring, Maryland
Silver Spring is an unincorporated area and census-designated place in Montgomery County, Maryland, United States. It had a population of 71,452 at the 2010 census, making it the fourth most populous place in Maryland, after Baltimore, Columbia, and Germantown.The urbanized, oldest, and...

 (whose postal area includes Wheaton
Wheaton, Maryland
Wheaton is an unincorporated, urbanized area in Montgomery County, Maryland, USA, north of Washington, D.C., northwest of Silver Spring. Wheaton takes its name from Frank Wheaton , a career officer in the United States Army and volunteer from Rhode Island in the Union Army who rose to the rank of...

) has its own prefix, 209, there was no need to apply the reshuffling to Silver Spring; instead, all mail going to 209xx ZIP codes was simply rerouted to the new sectional center facility.

On the other hand, depopulation may cause a post office to close and its associated ZIP code to be deallocated. For example, Centralia, Pennsylvania
Centralia, Pennsylvania
Centralia is a borough and ghost town in Columbia County, Pennsylvania, United States. Its population has dwindled from over 1,000 residents in 1981 to 12 in 2005, 9 in 2007, and 10 in 2010, as a result of a mine fire burning beneath the borough since 1962...

's ZIP code, 17927, was retired in 2002.

Elkins Park, Pennsylvania
Elkins Park, Pennsylvania
Elkins Park is an unincorporated community in Montgomery County, Pennsylvania, United States. It is split between Cheltenham and Abington Townships in the suburbs of Philadelphia, roughly from Center City, Philadelphia.-Points of interest:...

, was originally issued the 19117 ZIP code, although it lies in Montgomery County
Montgomery County, Pennsylvania
Montgomery County is a county located in the U.S. state of Pennsylvania, in the United States. As of 2010, the population was 799,874, making it the third most populous county in Pennsylvania . The county seat is Norristown.The county was created on September 10, 1784, out of land originally part...

. Because of the 191 prefix, which is found only in Philadelphia with that lone exception, auto insurance companies charged higher city premiums to that suburban location. For that reason, residents petitioned the USPS for a 190-prefix ZIP code, which is common to the inner-ring Pennsylvania suburbs of that city, and, after several attempts that were initially disapproved by the USPS, Elkins Park was finally reassigned to the 19027 ZIP code.

ZIP codes also change when postal boundaries are realigned. For example, at the same time at which the above-noted change in Montgomery County took place, and under pressure from then-mayor of Washington, D.C., Marion Barry
Marion Barry
Marion Shepilov Barry, Jr. is an American Democratic politician who is currently serving as a member of the Council of the District of Columbia, representing DC's Ward 8. Barry served as the second elected mayor of the District of Columbia from 1979 to 1991, and again as the fourth mayor from 1995...

, the USPS realigned the postal boundaries between the District of Columbia and Maryland to match the actual boundary. Previously, many inner suburbs, such as Bethesda
Bethesda, Maryland
Bethesda is a census designated place in southern Montgomery County, Maryland, United States, just northwest of Washington, D.C. It takes its name from a local church, the Bethesda Meeting House , which in turn took its name from Jerusalem's Pool of Bethesda...

 and Takoma Park
Takoma Park, Maryland
Takoma Park is a city in Montgomery County, Maryland, United States. It is a suburb of Washington, D.C., and part of the Washington Metropolitan Area. Founded in 1883 and incorporated in 1890, Takoma Park, informally called "Azalea City," is a Tree City USA and a nuclear-free zone...

, had been in the Washington, D.C., postal area. As a result of the change, ZIP codes in Maryland beginning with 200 were changed to new ZIP codes beginning with 207, 208 or 209, depending on their location, and ZIP codes straddling the D.C.-Maryland line were split. For example, 20014 (Bethesda) became 20814, while the Maryland portion of 20012 (Takoma Park) became 20912.

Delivery services

Delivery services other than the USPS, such as FedEx
FedEx
FedEx Corporation , originally known as FDX Corporation, is a logistics services company, based in the United States with headquarters in Memphis, Tennessee...

, United Parcel Service
United Parcel Service
United Parcel Service, Inc. , typically referred to by the acronym UPS, is a package delivery company. Headquartered in Sandy Springs, Georgia, United States, UPS delivers more than 15 million packages a day to 6.1 million customers in more than 220 countries and territories around the...

 and DHL
DHL
DHL Express is a division of the German logistics company Deutsche Post providing international express mail services. DHL is a world market leader in sea and air mail....

 require a ZIP code for optimal internal routing of a package.

Statistics

There are over 42,000 ZIP Codes in the United States. ZIP codes are used not only for tracking of mail but also in gathering geographical statistics in the United States. The U.S. Census Bureau
United States Census Bureau
The United States Census Bureau is the government agency that is responsible for the United States Census. It also gathers other national demographic and economic data...

 calculates approximate boundaries of ZIP Codes areas, which it calls ZIP Code Tabulation Area
ZIP Code Tabulation Area
ZIP Code Tabulation Areas are statistical entities developed by the United States Census Bureau for tabulating summary statistics from Census 2000. This new entity was developed to overcome the difficulties in precisely defining the land area covered by each ZIP code...

s (ZCTAs). Statistical census data is then provided for these approximate areas. The geographic data provided for these areas includes the latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

 and longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

 of the center-point of the ZCTAs
ZIP Code Tabulation Area
ZIP Code Tabulation Areas are statistical entities developed by the United States Census Bureau for tabulating summary statistics from Census 2000. This new entity was developed to overcome the difficulties in precisely defining the land area covered by each ZIP code...

. The Census Bureau provides many statistical data sets for ZIP Codes, but does not keep up-to-date datasets of all ZCTAs
ZIP Code Tabulation Area
ZIP Code Tabulation Areas are statistical entities developed by the United States Census Bureau for tabulating summary statistics from Census 2000. This new entity was developed to overcome the difficulties in precisely defining the land area covered by each ZIP code...

. Complete datasets providing a similar approximate geographic extent are commercially available.

ZIP Codes are inherently discrete data, or point based data, as they are assigned only at the point of delivery, not the spaces in between the delivery points. The U.S. Census Bureau
United States Census Bureau
The United States Census Bureau is the government agency that is responsible for the United States Census. It also gathers other national demographic and economic data...

 then interpolates this discrete data set to create polygons, or areal features representing the approximate extent of the ZIP Code to use for mapping and data presentation. ZCTAs
ZIP Code Tabulation Area
ZIP Code Tabulation Areas are statistical entities developed by the United States Census Bureau for tabulating summary statistics from Census 2000. This new entity was developed to overcome the difficulties in precisely defining the land area covered by each ZIP code...

 are not to be confused with ZIP codes, and they are not updated as frequently as ZIP Codes. However for many research and planning purposes they are very useful, and can be used with ZIP Code data.

Marketing

The data is often used in direct mail marketing campaigns in a process called ZIP-code marketing. Point-of-sale
Point of sale
Point of sale or checkout is the location where a transaction occurs...

 cashiers sometimes ask consumers their home ZIP code. Besides providing purchasing-pattern data useful in determining the location of new business establishments, retailers can use directories to correlate this ZIP code with the name on a credit card to obtain a consumer's full address and telephone number
Telephone number
A telephone number or phone number is a sequence of digits used to call from one telephone line to another in a public switched telephone network. When telephone numbers were invented, they were short — as few as one, two or three digits — and were given orally to a switchboard operator...

. ZIP-coded data are also used in analyzing geographic factors in risk, an insurance
Insurance
In law and economics, insurance is a form of risk management primarily used to hedge against the risk of a contingent, uncertain loss. Insurance is defined as the equitable transfer of the risk of a loss, from one entity to another, in exchange for payment. An insurer is a company selling the...

-industry
Industry
Industry refers to the production of an economic good or service within an economy.-Industrial sectors:There are four key industrial economic sectors: the primary sector, largely raw material extraction industries such as mining and farming; the secondary sector, involving refining, construction,...

 and banking practice pejorative
Pejorative
Pejoratives , including name slurs, are words or grammatical forms that connote negativity and express contempt or distaste. A term can be regarded as pejorative in some social groups but not in others, e.g., hacker is a term used for computer criminals as well as quick and clever computer experts...

ly known as redlining
Redlining
Redlining is the practice of denying, or increasing the cost of services such as banking, insurance, access to jobs, access to health care, or even supermarkets to residents in certain, often racially determined, areas. The term "redlining" was coined in the late 1960s by John McKnight, a...

. This can cause problems (e.g. expensive insurance) for people living near a town with a high crime rate and sharing its ZIP code, while they themselves actually live in a relatively crime-free town (see Elkins Park, Pennsylvania, above.)

According to an online CNN
CNN
Cable News Network is a U.S. cable news channel founded in 1980 by Ted Turner. Upon its launch, CNN was the first channel to provide 24-hour television news coverage, and the first all-news television channel in the United States...

 news story by Greg Botelho posted on Thursday, February 10, 2011, "California's high court ruled Thursday that retailers do not have the right to ask customers for their ZIP code while completing credit card transactions, saying that doing so violates a cardholders' right to protect his or her personal information."

Legislative districts

ZIP codes can be used to identify legislative districts. For example, the website of the U.S. House of Representatives has a "Find Your Representative" feature in the upper left corner based on ZIP code.

Internet

ZIP code data is an integral part of dealer/store locator software on many web sites, especially brick-and-click
Bricks and clicks
Bricks and clicks is a business model by which a company integrates both offline and online presences, sometimes with the third extra flips...

 websites. This software processes a user-input ZIP code and returns a list of store or business locations, usually in order of increasing distance from the center of the input ZIP code. As the ZIP system is confined to the U.S. Postal network, websites that require ZIP codes cannot register customers outside the U.S.

Credit card security

Many gasoline pumps that offer "pay at the pump" require credit card customers to enter the ZIP code of their billing address as a form of added security.
In New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

, when purchasing a MetroCard
MetroCard
The MetroCard is the payment method for the New York City Subway rapid transit system; New York City Transit buses, including routes operated by Atlantic Express under contract to the Metropolitan Transportation Authority ; MTA Bus, and MTA Long Island Bus systems; the PATH subway system; the...

 with a credit/debit card through a vending machine, the user is prompted to enter his/her zip code.

See also

  • J. W. Westcott II (the boat with its own zip code)
    J. W. Westcott II
    The J.W. Westcott II is a boat that serves to deliver mail to other vessels, and also provides a pilot boat service to ferry pilots to and from other vessels. The ship operates out of Detroit, Michigan and is the only floating post office in the world, that delivers mail to other ships, as they are...

  • Intelligent Mail Barcode
    Intelligent Mail Barcode
    The Intelligent Mail Barcode is a 65-bar code for use on mail in the United States. The term “Intelligent Mail” refers to services offered by the United States Postal Service for domestic mail delivery. is intended to provide greater information and functionality than its predecessors POSTNET and...

  • List of ZIP code prefixes
  • Postal Code
    Postal code
    A postal code is a series of letters and/or digits appended to a postal address for the purpose of sorting mail. Once postal codes were introduced, other applications became possible.In February 2005, 117 of the 190 member countries of the Universal Postal Union had postal code systems...

  • ZIP Code Tabulation Area
    ZIP Code Tabulation Area
    ZIP Code Tabulation Areas are statistical entities developed by the United States Census Bureau for tabulating summary statistics from Census 2000. This new entity was developed to overcome the difficulties in precisely defining the land area covered by each ZIP code...


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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