The Pentagon is the famous five-sided building, which serves as the headquarters of the United States Department of Defense. The building is located across the Potomac River from Washington D.C. in Arlington, Virginia, and is adjacent to the national cemetery. Constructed from 1941 to 1943, the Pentagon is the world’s largest office building. It was built to replace the War and Navy Department Building, which is now the Eisenhower Executive Office Building. More than 25,000 military and civilian personnel work inside the building each day.
Designed by George Bergstrom and built by general contractor John McShain, the structure is comprised of five rings that enclose a central courtyard. Each wing has five floors above ground. The project was over seen by Colonel Leslie Groves. Promoted to General shortly thereafter, Groves was placed in charge of the Manhattan Project, the program that built the atomic bomb. During the Cold War, the central courtyard was euphemistically referred to as ground zero under the belief that one or more Soviet nuclear missiles used it as an aiming point. The building suffered significant damage on September 11, 2001, 60 years to the day from the laying of the cornerstone. The damage was repaired with the same Indiana marble used in the original construction.
The term “the Pentagon” is commonly used to describe both the Department of Defense as well as the building.