The Pentagon

Overview

The Pentagon’s five-sided shape is not military symbolism. It is an accident of real estate. The design was drawn to fit the pentagon-shaped Arlington Farms tract below Arlington National Cemetery — but when objections arose that the massive new building would obstruct views of Washington, D.C. from the cemetery, the construction site was moved to the former Hoover Field airport instead. To keep costs down, the five-sided design plans were retained at the new, irregular site (PCAD; Arlington Tours). The most recognizable office building in the world looks the way it does because a cemetery asked it not to block the view.

What rose on that substitute site between 1941 and 1943 was the headquarters of the United States Department of Defense in Arlington, Virginia — a five-story, five-ring complex of 6,546,360 square feet, with 17.5 miles of corridors and a five-acre central courtyard, designed so that any point in the building could be reached within about ten minutes (PCAD). The building’s official postal address is in Washington, D.C. even though it physically stands in Arlington (PCAD). And “the Pentagon” has become the standard metonym for the American military institution itself — the department whose budget Congress writes at roughly a trillion dollars a year.

Built in 16 months, with almost no steel

The Pentagon was a wartime improvisation executed at wartime speed. The design process began on July 17, 1941; construction crews of 4,000 worked in three shifts, 24 hours a day, and the building was finished on January 15, 1943 — about 16 months after the September 11, 1941 groundbreaking (PCAD). The $31.1 million contract, let to three contractors, ended up costing slightly more than that figure (PCAD; Arlington Tours).

To save metal for the war effort, the architects avoided large steel beams entirely, building instead with reinforced concrete — about 680,000 tons of sand dredged from the Potomac River went into the mix, and the dredging created the artificial Pentagon Lagoon beside the site (PCAD). Steel was in such short supply that the design used ramps instead of elevators to move people between floors (Arlington Tours). The exterior was faced with Indiana limestone, and design and construction ran simultaneously, in sections, to save time (Arlington Tours).

The architects behind the building are themselves a story. Chief architect Edwin Bergstrom supervised the design and most of the construction — until April 11, 1942, when he was replaced by his partner David J. Witmer after Bergstrom became embroiled in a scandal while serving as president of the American Institute of Architects (PCAD). The Army officer overseeing the whole project was Colonel Leslie Groves, who would soon be put in charge of the Manhattan Project (Arlington Tours). And the building’s wartime origin is visible in its plumbing: Virginia’s segregation laws required separate rest rooms for Black and white workers, leaving the Pentagon with a higher ratio of rest rooms to occupants than comparable buildings — it was, in fact, the only public building in Arlington with segregated rest rooms until 1965 (Arlington Tours).

The Pentagon had been born of a space crisis: in 1941 the War Department had 24,000 employees scattered across Washington, and Secretary of War Henry Stimson lobbied President Franklin Roosevelt for one large permanent headquarters (Arlington Tours). The building it replaced in Foggy Bottom — constructed in the late 1930s and quickly outgrown — is currently used by the U.S. Department of State (Arlington Tours).

The institution: what the name has come to mean

Inside the rings, the E-ring — the only ring with exterior views — holds the offices of the most senior officials, and the five-acre central courtyard is nicknamed “Ground Zero” for the Cold War belief that it would be a primary target of Soviet nuclear missiles (Arlington Tours). The building was added to the National Register of Historic Places in 1989 (Arlington Tours).

As a metonym, the Pentagon’s scale is best measured in its annual authorization. When the House Armed Services Committee marked up the fiscal year 2026 defense policy bill, it voted 55–2 to authorize $882.6 billion in national defense spending, with $848.3 billion for the Defense Department — and when combined with the recently passed budget reconciliation bill, total national defense spending lands somewhere around $1 trillion, with $961 billion for the department (Inside Defense). The committee’s ranking Democrat is Rep. Adam Smith of Washington, who used the markup to push the Pentagon’s acquisition reforms and to boost Ukraine Security Assistance Initiative funding from $300 million to $400 million (Inside Defense).

The building’s darkest day is also the alliance system’s most consequential one. On September 11, 2001 — exactly 60 years after construction began — American Airlines Flight 77 struck the Pentagon’s west side, killing 184 people in the building and aboard the plane (PCAD; Arlington Tours). Repairs were completed by the first anniversary of the attack (Arlington Tours). The day after the attacks on the World Trade Center and the Pentagon, NATO invoked Article 5 for the first — and so far only — time in its history, committing its members to stand by the United States (HISTORY).

The renovation the building desperately needed

By the 1990s, the wartime wonder was failing its own occupants. The full-scale Pentagon Renovation Program, begun in 1994, found that the building did not meet fire, safety or health codes, had no sprinklers, and — because of outdated electrical systems — experienced 20 to 30 power outages daily (PCAD). After the 2001 terrorist attack, a rapid rebuilding effort called the “Phoenix Project” was folded into the renovation program (PCAD). The broader program wrapped up around 2010–2011, bringing the 1940s building up to modern office standards (PCAD; Arlington Tours).

What this profile does not claim

This profile does not assert a single current workforce figure — sources give ~23,000 (2017) and “nearly 30,000,” and neither is claimed as today’s number. It does not give the 9/11 toll as 189 without qualification: 184 people died in the building and on the plane, a figure that excludes the five hijackers. It does not state the Pentagon’s precise current budget, only the FY2026 authorization figures reported by Inside Defense. The renovation-completion date differs slightly between sources (1994–2010 vs. completed 2011) and is not stated as a single settled year. The E-ring seniority and “Ground Zero” nickname rest on a single tier3 source. And nothing here predicts future defense spending or the outcome of the 2026 oversight fights over the Pentagon’s leadership.