The Pentagon was built in 1943 in Arlington, Virginia, across the Potomac River from Washington. It occupies some 6.5 million square feet and houses roughly 23,000 civilian and military employees. During the 9/11 terrorist attacks, the hijacked American Airlines Flight 77 crashed into the side of the building, killing 189 people. The term "the Pentagon" is often used to refer to the US Defense Department as a whole. Here is a collection of all of DW's content on the Pentagon.