The Architectural History Of The Pentagon

"On a warm and rainy Thursday evening in July 1941, inside a War Department office in Washington, a small group of Army officers hastily assembled for a meeting and listened in disbelief to the secret plan outlined by their commander, Brig. Gen. Brehon Burke Somervell"

"The War Department needed a new headquarters, Somervell said. Somervell wanted a headquarters big enough to hold 40,000 people, with parking for 10,000 cars. It would contain 4 million square feet of office space -- almost twice as much as the Empire State Building."

"The easiest solution, constructing a tall building, was out. They would have to spread out horizontally. But how? A square building that size -- with the enormous interior distances to be covered -- was too unwieldy, as was a rectangle. The Arlington Farm tract had a peculiar asymmetrical pentagon shape bound on five sides by roads or other divisions. Finally, guided by the odd shape of the plot, they designed an irregular pentagon."