History of the United States (1991–2008) South Tower less than twenty minutes later at 9:03 A.M. (EST), resulting in the collapse of both 110 story skyscrapers, and the destruction of the World Trade Center. The third hijacked plane, American Airlines Flight 77, was crashed into the Pentagon (the headquarters of the United States Department of Defense) in Arlington County, Virginia, demolishing a section of the outer southwest facing wall. After discovering that their plane, United Airlines Flight 93, was going to be used as a missile, passengers attempted to regain control of the plane which had been redirected towards Washington, D.C. However, after regaining control from
Arlington County, Virginia county having the same name, a movement started to rename Alexandria County. In 1920, the name Arlington County was adopted, after Arlington House, the home of the American Civil War Confederate general Robert E. Lee, which stands on the grounds of what is now Arlington National Cemetery. The Town of Potomac was incorporated as a town in Alexandria County in 1908. The town was annexed by the independent city of Alexandria in 1930. In 1896, an electric trolley line was built from Washington through Ballston, which led to growth in the county (see Northern Virginia trolleys). In 1920, the Virginia