AKA: U.S. Defense Department, the Pentagon, Arlington, VA

Structure Type: built works - military buildings

Designers: Bergstrom and Witmer, Architects (firm); George Edwin Bergstrom (architect); David Julius Witmer (architect)

Dates: constructed 1941-1943

5 stories, total floor area: 6,546,360 sq. ft.

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1400 Defense Pentagon
Washington, DC 22202

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While the Pentagon is physically situated in Arlington, VA, its official postal address is in Washington, DC.


In 2017, about 23,000 defense workers and members of the military worked in the Pentagon. It covered about 29 acres across the Potomac River from the nation's capital. The building's five-sided shape had been tailored to fit a pentagonal-shaped building site below Arlington National Cemetery, but this original location was changed due to objections that the massive new building would obstruct views of the city from the cemetery. A new site, pieced together from 80 acres of Fort Myer (founded as Fort Whipple in 1863) and approximately147 acres from the Washington-Hoover Airport (opened in 07/1926 and closed in 1941), was found in what had been a notorious, low-income neighborhood, nicknamed "Hell's Bottom." This largely African-American residential section was rapidly leveled to make way for this crucial military center during World War II. The Pentagon remained in 2017 one of the world's largest, low-rise office buildings, with 17.5-miles of corridors, 3.7 million square feet of office space, and a five-acre central courtyard. It was designed originally to accommodate 33,000 wartime workers.

Building History

The design process began 07/17/1941 and construction finished on 01/15/1943; Working in three shifts, construction crews numbering 4,000 worked 24 hours per day to finish the 6,546,360 square-foot office building housing offices for the U.S. military. Five stories tall, the design enables any point to be reached within ten minutes. Ironically, ground was broken for the Pentagon on 09/11/1941, exactly 70 years before Al Qaeda terrorists crashed American Airlines Flight 77 into the facility. A contract for $31,100,000 was let to three contractors, the main being John McShain, Incorporated, of Philadelphia, PA, assisted by Wise Contracting Company, Incorporated, and Doyle and Russell, Building Contractors, both from VA.

Chief Architect Edwin Bergstrom (1876-1955) supervised the design and most of the construction of the Pentagon. He was replaced by his partner, David J. Witmer (1888-1973), as Chief on 04/11/1942, when Bergstrom became embroiled in a scandal while he was President of the American Institute of Architects (AIA).

Building Notes

In order to save metal for war-time uses, the architects avoided using large steel beams, depending, instead, on reinforced concrete. Steel was still used to reinforce the concrete, but spanning members were not specified to be metallic. About 680,000 tons of sand dredged from the Potomac River was used to produce the concrete.


Between 1994-2010, a full-scale renovation known officially as the "Pentagon Renovation Program," has resulted in the gradual replacement of old ventilation equipment and removal of asbestos. According to Smithsonian.com: "The building renovation was sorely needed, says Mahan. When the overhaul began in 1994, the Pentagon did not meet fire, safety or health codes, had no sprinklers, and because of outdated electrical systems, experienced 20-to-30 power outages daily. Workers can get coffee at Starbucks, an ice cream at Baskin-Robbins, or a bucket to go at KFC—all of which are located within the complex." (See Alicia Ault, Smithsonian.com, "Why Is the Pentagon a Pentagon?" published 04/10/2017, accessed 05/15/2017.)

When originally built, the Pentagon relied on windows with cross-ventilation for cooling; recently, windows have been sealed to maximize air-conditioning effectiveness. After the terrorist attack of 09/11/2001, a rapid rebuilding project, called the "Phoenix Project ," was added to the existing renovation program.

PCAD id: 5004