The Pentagon is the headquarters of the United States Department of Defense

United States Department of Defense

The United States Department of Defense is the U.S...

, located in Arlington County

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...

, 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...

. As a symbol of the U.S. military

United States armed forces

The United States Armed Forces are the military forces of the United States. They consist of the Army, Navy, Marine Corps, Air Force, and Coast Guard.The United States has a strong tradition of civilian control of the military...

, "the Pentagon" is often used metonymically

Metonymy

Metonymy is a figure of speech used in rhetoric in which a thing or concept is not called by its own name, but by the name of something intimately associated with that thing or concept...

 to refer to the Department of Defense rather than the building itself.

Designed by the American architect George Bergstrom

George Bergstrom

George Edwin Bergstrom was an American architect most noted for his design work on the Pentagon in Arlington County, Virginia.-Background:...

 (1876–1955), and built by Philadelphia, Pennsylvania, general contractor John McShain

John McShain

John McShain was a highly successful American building contractor known as "The Man Who Built Washington."...

, the building was dedicated on January 15, 1943, after ground was broken for construction on September 11, 1941.