Before the Pentagon was built, the United States Department of War was headquartered in the Munitions Building, a temporary structure erected during World War I along Constitution Avenue on the National Mall.
The War Department, which was a civilian agency created to administer the U.S. Army, was spread out in additional temporary buildings on the National Mall, as well as dozens of other buildings in Washington, D.C., Maryland and Virginia.
In the late 1930s, a new War Department Building was constructed at 21st and C Streets in Foggy Bottom but, upon completion, the new building did not solve the department's space problem and ended up being used by the Department of State.
When World War II broke out in Europe, the War Department rapidly expanded in anticipation that the United States would be drawn into the conflict.
Secretary of War Henry L. Stimson found the situation unacceptable, with the Munitions Building overcrowded and the department spread out.

Stimson told U.S. President Franklin D. Roosevelt in May 1941 that the War Department needed additional space.
On 17 July 1941, a congressional hearing took place, organized by Virginia congressman Clifton Woodrum, regarding proposals for new War Department buildings.
Woodrum pressed Brigadier General Eugene Reybold, who was representing the War Department at the hearing, for an "overall solution" to the department's "space problem" rather than building yet more temporary buildings.
Reybold agreed to report back to the congressman within five days.
The War Department called upon its construction chief, General Brehon Somervell, to come up with a plan.
Before the Pentagon was built, the United States Department of War was headquartered in the Munitions Building, a temporary structure erected during World War I along Constitution Avenue on the National Mall. The War Department, which was a civilian agency created to administer the U.S. Army, was spread out in additional temporary buildings on the National Mall, as well as dozens of other buildings in Washington, D.C., Maryland and Virginia. In the late 1930s, a new War Department Building was constructed at 21st and C Streets in Foggy Bottom but, upon completion, the new building did not solve the department's space problem and ended up being used by the Department of State. When World War II broke out in Europe, the War Department rapidly expanded in anticipation that the United States would be drawn into the conflict. Secretary of War Henry L. Stimson found the situation unacceptable, with the Munitions Building overcrowded and the department spread out.
Stimson told U.S. President Franklin D. Roosevelt in May 1941 that the War Department needed additional space. On 17 July 1941, a congressional hearing took place, organized by Virginia congressman Clifton Woodrum, regarding proposals for new War Department buildings. Woodrum pressed Brigadier General Eugene Reybold, who was representing the War Department at the hearing, for an "overall solution" to the department's "space problem" rather than building yet more temporary buildings. Reybold agreed to report back to the congressman within five days. The War Department called upon its construction chief, General Brehon Somervell, to come up with a plan.
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