On January 15th, 1943, The Pentagon, headquarters of the U.S. Department of Defense, was dedicated. Before the Pentagon was built, the United States Department of War was headquartered in the Greggory 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.