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 Arlington County, Virginia Arlington County is a county in the Commonwealth of Virginia, often referred to simply as Arlington or Arlington, Virginia. In 2016, the county's population was estimated at 230,050, making it the sixth-largest county in Virginia, or the fourth-largest city if it were incorporated as such. It is the 5th highest-income county in the U.S. by median family income, and has the highest concentration of singles in the region. The county is coterminous with the U.S. Census Bureau's census-designated place of Arlington. Though a county, it is also treated as the second-largest principal city of the Washington metropolitan