The Pentagon

Administrative building in Arlington, Virginia The Pentagon is the headquarters of the United States Department of Defense, located in Arlington County, Virginia, across the Potomac River from Washington, D.C. As a symbol of the U.S. military, The Pentagon is often used metonymically to refer to the U.S. Department of Defense. On September 11, 2001, exactly 60 years after the building's construction began, American Airlines Flight 77 was hijacked and flown into the western side of the building, killing 189 people (59 victims and the five perpetrators on board the airliner, as well as 125 victims in the building), according to the official report. It was the first significant foreign attack on Washington's governmental facilities since the city was burned by the British during the War of 1812.