The Pentagon is located in Arlington County, Va., in the United States. It is located near the national capital, Washington, D.C. The Pentagon is a large five-sided building and is home to the U.S. Department of Defense headquarters.
The Pentagon is the headquarters of the three branches of the U.S. military: the Navy, the Army and the Air Force. The building was erected between 1941 and 1943 and was originally designed as the headquarters for the U.S. War Department. The Pentagon has five floors, including a basement and a mezzanine level. It was attacked by terrorists flying a commercial airliner in 2001.