The iconic Pentagon building is recognized around the globe as home to the United States Department of Defense. But did you know the star-shaped structure is also the world’s largest office building and was formed with sand and gravel scooped from the Potomac River?
LIFE has published previously-unseen photos of the Pentagon’s construction, offering an intimate glimpse behind the scenes of the ambitious project.
The Pentagon building was conceived during the tense period leading up to the United States’ entrance into World War II. In 1941, the U.S. Army was run by the War Department—the precursor to the Department of Defense, which did not exist until 1949.
At that time, according to the Washington Post, “The War Department in Washington was growing at an explosive rate, its 24,000 workers spread in 17 buildings, including apartment buildings, private homes and several rented garages.”
The goal was to consolidate the 17 buildings of the War Department into one large building.
Construction began on September 11, 1941 in Arlington, Virginia, close to the Potomac River. According to the Pentagon website, the original site was “nothing more than wasteland, swamps and dumps.”
To build the foundation, 5.5 million cubic yards of earth, and 41,492 concrete piles were needed. Forming the Pentagon-shaped structure involved pulling 680,000 tons of sand and gravel from the Potomac River and processing it into concrete.
Only 16 months later, the building was complete, costing taxpayers approximately $83 million. The finished building included seven floors (five of them above the ground and two beneath), almost 18 miles of corridors and 131 stairways.
Today, approximately 23,000 employees work in the Pentagon.
Below are two of the never-before released photos. Check out the entire series of photos here.
Architects and draftsmen work on plans for the Pentagon's construction.
Workers constructing the building.