The Pentagon The Pentagon The Pentagon, in Arlington County, Virginia, across the Potomac River from Washington, D.C., is the headquarters of the United States Department of Defense. As a symbol of the U.S. military, the phrase "The Pentagon" is often used as a metonym for the Department of Defense and its leadership. The building was designed by American architect George Bergstrom and built by contractor John McShain. Ground was broken on September 11, 1941, and the building was dedicated on January 15, 1943. General Brehon Somervell provided the major motivating power behind the project; Colonel Leslie Groves was responsible for overseeing the
Arlington County, Virginia property. (Ultimately, the name is a variant of Harlington, London, seat of the first Baron of Arlington; it in turn derives from Hygerǣd, an Anglo-Saxon noble's name.) George Washington Parke Custis, grandson of First Lady Martha Washington, acquired this land in 1802. The estate was eventually passed down to Mary Anna Custis Lee, wife of General Robert E. Lee. The property later became Arlington National Cemetery during the American Civil War, and eventually lent its name to present-day Arlington County. The area that now contains Arlington County was ceded to the new United States federal government by Virginia. With the