The Washington Monument is an obelisk

Obelisk

An obelisk is a tall, four-sided, narrow tapering monument which ends in a pyramid-like shape at the top, and is said to resemble a petrified ray of the sun-disk. A pair of obelisks usually stood in front of a pylon...

 near the west end of the National Mall

National Mall

The National Mall is an open-area national park in downtown Washington, D.C., the capital of the United States. The National Mall is a unit of the National Park Service , and is administered by the National Mall and Memorial Parks unit...

 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....

, built to commemorate the first U.S. president, General George Washington

George Washington

George Washington was the dominant military and political leader of the new United States of America from 1775 to 1799. He led the American victory over Great Britain in the American Revolutionary War as commander-in-chief of the Continental Army from 1775 to 1783, and presided over the writing of...

. The monument, made of marble

Marble

Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite.Geologists use the term "marble" to refer to metamorphosed limestone; however stonemasons use the term more broadly to encompass unmetamorphosed limestone.Marble is commonly used for...

, granite

Granite

Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...

, and bluestone gneiss

Gneiss

Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks.-Etymology:...

, is both the world's tallest stone structure and the world's tallest obelisk, standing 555 foot.
There are taller monumental columns, but they are neither all stone nor true obelisks. group=n name=column>The Washington Monument is the third tallest monumental column in the world after the San Jacinto Monument

San Jacinto Monument

The San Jacinto Monument is a high column located on the Houston Ship Channel in unincorporated Harris County, Texas near the city of La Porte. The monument is topped with a 220-ton star that commemorates the site of the Battle of San Jacinto, the decisive battle of the Texas Revolution...

 in 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...

 and the Juche Tower

Juche Tower

The Juche Tower is a monument in Pyongyang, North Korea. The tower is named after the principle of Juche, developed by Kim Il Sung as a blend of autarky, self-reliance, nationalism, isolationism, Korean traditionalism, and Marxism-Leninism.Completed in 1982, it is sited on the eastern bank of the...

 in North Korea

North Korea

The Democratic People’s Republic of Korea , , is a country in East Asia, occupying the northern half of the Korean Peninsula. Its capital and largest city is Pyongyang. The Korean Demilitarized Zone serves as the buffer zone between North Korea and South Korea...

.

• The San Jacinto Monument is taller by 11.9 feet (3.6 m), but it is made of reinforced concrete
  Reinforced concrete
  Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...
  
  , not stone, even though it has a facade of limestone.
• The Juche Tower is taller by less than a meter, but its top 20 meters are metal, not stone.

It is also the tallest structure in Washington D.C. It was designed by Robert Mills

Robert Mills (architect)

Robert Mills , most famously known for designing the Washington Monument, is sometimes called the first native born American to become a professional architect, though Charles Bulfinch perhaps has a clearer claim to this honor...

, an architect

Architect

An architect is a person trained in the planning, design and oversight of the construction of buildings. To practice architecture means to offer or render services in connection with the design and construction of a building, or group of buildings and the space within the site surrounding the...

 of the 1840s.