Science Fair Project Encyclopedia
The Pentagon is the headquarters of the United States Department of Defense. It was dedicated on January 15, 1943 and it is the world's largest office building. Those who work within its walls often simply call it "The Building", "Fort Fumble" or the "Puzzle Palace".
The building is pentagon-shaped in plan and houses approximately 23,000 military and civilian employees and about 3,000 non-defense support personnel in Arlington, Virginia, just outside Washington, DC. It has five floors and each floor has five ring corridors.
Built during the early years of World War II, with construction supervised by the future Manhattan Project supervisor Leslie Groves, it is still thought of as one of the most efficient office buildings in the world. Despite 17.5 miles (28 km) of corridors it takes a maximum of seven minutes to walk between any two points in the building.
It was built from 680,000 tons of sand and gravel dredged from the nearby Potomac River that were processed into 435,000 cubic yards (330,000 m³) of concrete and molded into the pentagon shape. Very little steel was used in its design due to the needs of the war effort.
At five acres (20,000 m²), the central plaza in the Pentagon is the largest "no-salute, no-cover" area (where hats need not be worn and salutes are not required) in the world. The open space in the center is informally known as ground zero, a nickname originating during the Cold War when it was thought of as the most likely target of a nuclear missile. At the center of the plaza is the "Ground Zero Cafe," a snack bar. One 'legend' states that due to the heavy traffic into this cafe (evidenced by satellite imagery), Soviet intelligence concluded it was a center for highly secret research.
Sixty years to the day after groundbreaking on the Pentagon, the September 11, 2001 attacks occurred. American Airlines Flight 77 crashed into the building, causing part of it to collapse and killing 125 people in addition to the 64 aboard the plane. For pictures and graphics showing the damage in the impact see this briefing.
Contractors who had been in the midst of upgrading the building as part of a major renovation , were quickly assigned to repair the building. Part of the renovation involved adding improved security features, including walls and windows with greater blast resistance. The aircraft struck on the edge between two sections—one of which had just finished being upgraded. An initial analysis suggested that the section's improvements had helped mitigate the damage somewhat. The first of the workers whose offices were destroyed or damaged in the attack began moving back in on August 15, 2002. 
Just south of the Pentagon are Pentagon City and Crystal City, extensive shopping and high-density residential districts in Arlington. Arlington National Cemetery is to the north. A Washington Metro station is also located at the Pentagon, on the Blue and Yellow Lines.
Facts & figures
- Total land area: 583 acres (2.4 km²)
- Cost: $2,245,000
- Area covered by Pentagon bldg: 29 acres (117,000 m²)
- Area of center court: 5 acres (20,000 m²)
- Access highways built: 30 miles (48 km)
- Overpasses and bridges built: 21
- Parking space: 67 acres (270,000 m²)
- Capacity (vehicles): 8,770
- Main building
- Cost of building: $49,600,000
- Gross floor area: 6,636,360 ft² (620,000 m²)
- Cubic contents: 77,015,000 ft³ (2,000,000 m³)
- Length of each outer wall: 921 ft (280 m)
- Height of building: 77 ft 3.5 in (24 m)
- Number of floors, plus mezzanine and basement: 5
- Total length of corridors: 17.5 mile (28 km)
- Number of:
- Stairways: 131
- Escalators: 19
- Elevators: 13
- Rest rooms: 284 (Twice as many as necessary, due to Virginia segregation laws that were still in effect when built.)
- Fixtures: 4,900
- Drinking fountains: 691
- Clocks installed: 4,200
- Light fixtures: 16,250
- Windows: 7,754
- Great Buildings Online - The Pentagon
- The Pentagon website
- United States Department of Defense website
- Max X. Miller Online's September 11th Memorial
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