.
. As a symbol of the
for the Department of Defense and its leadership.
. Ground was broken on
. General
.
Before the Pentagon was built, the
United States Department of War was headquartered in the
Munitions Building, a temporary structure erected during
World War I along
Constitution Avenue on the
National Mall. The War Department, which was a civilian agency created to administer the
U.S. Army, was spread out in additional temporary buildings on the National Mall, as well as dozens of other buildings in Washington, D.C.,
Maryland and
Virginia. In the late 1930s, a
new War Department Building was constructed at 21st and C Streets in
Foggy Bottom but, upon completion, the new building did not solve the department's space problem and ended up being used by the
Department of State. When
World War II broke out in Europe, the War Department rapidly expanded in anticipation that the United States would be drawn into the conflict. Secretary of War
Henry L. Stimson found the situation unacceptable, with the Munitions Building overcrowded and the department spread out.
The Pentagon is the world's
largest office building, with about 6,500,000 square feet (150 acres; 0.60 km2) of
floor space, of which 3,700,000 sq ft (85 acres; 0.34 km2) are used as offices. Some 23,000
military and
civilian employees, and another 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 miles (28.2 km) of corridors. The central five-acre (2.0 ha) pentagonal plaza is nicknamed "
ground zero" on the presumption that it would be a prime target in a
nuclear war.
On
11 September 2001,
American Airlines Flight 77 was
hijacked and flown into the western side of the building, killing 189 people. Of those killed, 64 were on the hijacked airplane, and 125 were in the Pentagon. It was the first significant foreign attack on Washington's governmental facilities since
the city was burned by the British during the
War of 1812.