It is a massive concrete five-sided puzzle sitting just across the Potomac. Most people see the Pentagon as a symbol of American military might, but honestly, the building of the Pentagon was more about frantic necessity than grand architecture. It was born out of a desperate need for space during a time when the world was literally on fire. In the summer of 1941, the War Department was scattered across 17 different buildings in Washington, D.C. They were overflowing. Some people were working in temporary wooden shacks left over from World War I. General George C. Marshall basically told his staff they needed a single roof, and they needed it yesterday.
They built it fast. Unbelievably fast.
Construction started on September 11, 1941. That date is a weird, haunting coincidence in American history, isn't it? Sixteen months later, the whole thing was done. For a building that spans over 6 million square feet, that’s just insane. Most modern office buildings take longer to get through the zoning board than it took for the U.S. Army to dump millions of tons of sand and gravel into a swamp and call it a headquarters.
A Swamp, a Reformatory, and Too Much Mud
The site selection for the building of the Pentagon wasn't exactly a high-end real estate play. The land was originally a mix of swampland, a defunct landing field, and an old experimental farm. It was known as "Hell’s Bottom." There was also a neighborhood there called Queen City, which was home to a vibrant Black community. To make room for the massive footprint, the government essentially bulldozed the neighborhood, displacing hundreds of families. This is one of those darker chapters that people often gloss over when they talk about the "miracle" of the construction.
The ground was terrible. It was soft, silty mud.
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Engineers under Brigadier General Brehon Somervell had to drive roughly 41,492 concrete piles into the muck to keep the building from sinking into the river. They couldn't use much steel because, by 1941, every scrap of metal was being diverted to build tanks, ships, and planes for the war effort. So, they used reinforced concrete. Lots of it. 680,000 tons of sand and gravel were dredged directly from the Potomac River to make the mix. If you look at the walls today, you're looking at the literal bottom of the riverbed.
Why five sides?
You’ve probably wondered why it isn't a square or a circle. The shape was dictated by the original site. At first, they were going to build it on a piece of land called Arlington Farms, which was bordered by five existing roads. The architects, led by George Bergstrom, designed a pentagon to fit that specific plot. But then, President Franklin D. Roosevelt got worried that the building would block the view of Washington from Arlington National Cemetery. He moved the site downstream to the current location, but they kept the five-sided design.
Why keep it?
Because they didn't have time to redraw the blueprints. They were in such a rush that the design was being finished while the foundations were already being poured. Changing to a square would have set them back weeks. So, we ended up with a five-sided building on a site where a square would have fit just fine. It was a choice born of pure, unadulterated haste.
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Segregation in the Walls
If you walk through the Pentagon today, you'll notice something odd about the bathrooms. There are way too many of them. During the building of the Pentagon, Virginia was still a segregated state. Even though it was a federal building, the designers followed local Jim Crow laws. They built separate restrooms and separate cafeterias for white and Black workers.
When FDR visited the site during construction, he was reportedly stunned by the number of bathrooms. He eventually signed Executive Order 8802, which prohibited racial discrimination in the national defense industry. Because of that, the Pentagon was never actually segregated in practice once it opened, but the physical evidence—the double the number of toilets—is baked into the very architecture of the hallways. It stands as a silent witness to the social friction of the 1940s.
The Logistics of a Five-Acre Center
Walking from one side of the building to the furthest point on the opposite side takes about seven minutes. That's it. This is the real genius of the concentric ring design. Despite the building being so massive that you could fit the entire U.S. Capitol into any one of its five wedges, the layout is incredibly efficient.
- 17.5 miles of hallways wind through the structure.
- The center courtyard is roughly five acres, and it's known as "Ground Zero" because it was assumed that during the Cold War, a Soviet nuclear missile would be aimed directly at the center of the park.
- No elevators were used in the original construction. They used ramps instead. This was partially to save steel and partially to make it easier to move heavy equipment and carts between the five floors.
Reality Check: The Cost of Speed
Was it a "good" deal? The original budget was roughly $35 million. By the time they finished, it cost around $83 million. In 1943 dollars, that was a staggering amount of money. But they got what they wanted. They got a central brain for the most powerful military force in human history, completed in roughly 490 days.
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The building of the Pentagon was a gamble that paid off during World War II, but it created a maintenance nightmare for the future. Because it was built so fast with "unwashed" river silt, the concrete began to deteriorate over the decades. The building eventually underwent a massive, multi-billion dollar renovation (the Phoenix Project) that took far longer—over a decade—than the original construction itself.
The 9/11 Connection and Reinforcement
When Flight 77 struck the Pentagon in 2001, the building's structural integrity was put to the ultimate test. Ironically, the section that was hit had just been reinforced during the renovation process. The steel-reinforced concrete and blast-resistant windows saved hundreds of lives that day. The way the building was designed—those concentric rings—actually acted as a series of barriers that prevented the plane from traveling further into the heart of the structure.
What to Keep in Mind Moving Forward
If you're researching the building of the Pentagon for historical or architectural reasons, you have to look past the "heroic" narrative of the 1940s. It was a project defined by compromise.
- Check the Archives: If you want the real, gritty details of the daily construction logs, the National Archives (RG 330) holds the primary records of the Office of the Secretary of Defense. You'll see the frantic memos about missing shipments of gravel and the arguments over the height of the building.
- Visit the Memorial: If you’re ever in D.C., go to the 9/11 Memorial on the west side. You can see the difference in the stone where the building was repaired. The new limestone came from the same quarry in Indiana as the original 1941 stone to ensure a match, but the "new" section is a reminder that this building is a living history, not just a relic.
- Architectural Context: Look into the work of George Bergstrom. He resigned before the project was even finished due to unrelated controversies, but his vision of a "horizontal skyscraper" changed how we think about office logistics forever.
The Pentagon isn't just a building; it's a 29-acre footprint of 1941’s anxieties, prejudices, and engineering brashness. It’s a miracle it stands at all, considering it was built on a foundation of river mud and wartime pressure. If you want to understand American power, stop looking at the flags and start looking at the concrete. It tells a much more honest story.
Next Steps for Deep Research:
- Review the Library of Congress Digital Collections for photographs of "Hell's Bottom" prior to 1941 to see the displacement of Queen City.
- Consult the U.S. Army Center of Military History for the official monograph on the construction logistics.
- Search for Indiana Limestone Company records to understand why that specific material was chosen for the exterior facade.