THROWBACKTHISDAY, JAN 15; World's largest office building, Pentagon, completed

                           

The Pentagon is the headquarters of the United States Department of Defense, located in Arlington County, Virginia. As a symbol of the U.S. military, "The Pentagon" is often used metonymically to refer to the U.S. Department of Defense.

The Pentagon was designed by American architect George Bergstrom (1876–1955), and built by general contractor John McShain of Philadelphia .The building was dedicated on January 15, 1943. General Brehon Somervell provided the major motive power behind the project; Colonel Leslie Groves was responsible for overseeing the project for the U.S. Army.

The Pentagon is a large office building, with about 6,500,000 sq ft (600,000 m²), of which 3,700,000 sq ft (340,000 m²) are used as offices.Approximately 23,000 military and civilian employees and about 3,000 non-defense support personnel work in the Pentagon. It has five sides, five floors above ground, two basement levels, and five ring corridors per floor with a total of 17.5 mi (28.2 km) of corridors. The Pentagon includes a five-acre (20,000 m²) central plaza, which is shaped like a pentagon and informally known as "ground zero," a nickname originating during the Cold War on the presumption that it would be targeted by the Soviet Union at the outbreak of nuclear war.

On September 11, 2001, exactly 60 years after the building's construction began, American Airlines Flight 77 was hijacked and flown into the western side of the building, killing 189 people (59 victims and the five perpetrators on board the airliner, as well as 125 victims in the building). It was the first significant foreign attack on Washington, D.C.'s governmental facilities since the burning of Washington during the War of 1812.

THROWBACKTHISDAY; makes it 73 years and TBT Blog remembers.