The Alton Junction, more commonly known as the 21st Street Crossing, is a historically significant rail location in Chicago, 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,...

. The junction can be found just east of Canal Street and north of Cermak Road

Cermak Road

Cermak Road, formerly 22nd Street, is a major east-west artery on Chicago's south side and western suburbs. It is named for assassinated Chicago mayor Anton Cermak.-Points of interest:...

 near Chicago's Chinatown

Chinatown, Chicago

The Chinatown neighborhood in Chicago, Illinois, is on the South Side , centered on Cermak and Wentworth Avenues, and is an example of an American Chinatown, or ethnic-Chinese neighborhood. By the [ftp://ftp2.census.gov/census_2000/datasets/demographic_profile/Illinois/2kh17.pdf 2000 Census], has...

. It is located just south of a massive vertical lift bridge that spans the South Branch of the Chicago River

Chicago River

The Chicago River is a system of rivers and canals with a combined length of that runs through the city of the same name, including its center . Though not especially long, the river is notable for being the reason why Chicago became an important location, as the link between the Great Lakes and...

 and "guards" the entrance to Chicago's Union Station

Union Station (Chicago)

Union Station is a major train station that opened in 1925 in Chicago, replacing an earlier 1881 station. It is now the only intercity rail terminal in Chicago, as well as being the city's primary terminal for commuter trains. The station stands on the west side of the Chicago River between Adams...

. While a significant amount of rail traffic still traverses this interlock everyday, it has been greatly reduced from using 26 diamonds

Level junction

In U.S. railroad practice, a level junction is a railway junction that has a track configuration in which merging or crossing railroad lines provide track connections with each other that require trains to cross over in front of opposing traffic at grade In U.S. railroad practice, a level junction...

 to control over 150 trains using the crossing.

The north-south line is the former Pennsylvania Railroad (Pittsburgh, Fort Wayne & Chicago

Pittsburgh, Fort Wayne and Chicago Railway

The Pittsburgh, Fort Wayne and Chicago Railway was a major part of the Pennsylvania Railroad system, extending the PRR west from Pittsburgh, Pennsylvania via Fort Wayne, Indiana to Chicago, Illinois...

) mainline, which is now owned and operated by Amtrak

Amtrak

The National Railroad Passenger Corporation, doing business as Amtrak , is a government-owned corporation that was organized on May 1, 1971, to provide intercity passenger train service in the United States. "Amtrak" is a portmanteau of the words "America" and "track". It is headquartered at Union...

 as the southern gateway to the Union Station complex. The Norfolk Southern

Norfolk Southern Railway

The Norfolk Southern Railway is a Class I railroad in the United States, owned by the Norfolk Southern Corporation. With headquarters in Norfolk, Virginia, the company operates 21,500 route miles in 22 eastern states, the District of Columbia and the province of Ontario, Canada...

's Chicago Line

Chicago Line

The following rail lines are known as the Chicago Line:*Conrail's Chicago Line, Chicago to Albany, now the following Norfolk Southern and CSX lines:**Chicago Line , Chicago to Cleveland**Cleveland Terminal Subdivision , Cleveland...

 terminates at the southern entrance to the interlocking, but both NS and Burlington Northern Santa Fe

BNSF Railway

The BNSF Railway is a wholly owned subsidiary of Berkshire Hathaway Inc., and is headquartered in Fort Worth, Texas. It is one of seven North American Class I railroads and the second largest freight railroad network in North America, second only to the Union Pacific Railroad, its primary...

 trains have trackage rights over the bridge to access the BNSF east-west main line. All of Amtrak's East Coast bound and Michigan

Michigan Services

Michigan Services is an umbrella term used by Amtrak to describe passenger rail service by three routes connecting Chicago, Illinois, with the Michigan cities of Grand Rapids, Port Huron, and Detroit, and other stations along the three lines...

 trains use this track. The east-west line now belongs to the Canadian National Railway

Canadian National Railway

The Canadian National Railway Company is a Canadian Class I railway headquartered in Montreal, Quebec. CN's slogan is "North America's Railroad"....

. It at one time was owned by Illinois Central

Illinois Central Railroad

The Illinois Central Railroad , sometimes called the Main Line of Mid-America, is a railroad in the central United States, with its primary routes connecting Chicago, Illinois with New Orleans, Louisiana and Birmingham, Alabama. A line also connected Chicago with Sioux City, Iowa...

 and was the carrier's route out of its Central Station to Iowa.

Alton Junction was controlled by a manned interlocking tower until 2005 when Amtrak transferred control to its new Chicago Terminal control center. Known as 21st Street tower, its operators handled movements through the busy plant using a US&S Model 14 electro-pneumatic interlocking machine. In its final years 21st St took remote control of the closed Amtrak Clara St tower in New Orleans. In 2006 the closed brick tower was demolished.