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 2018 ParkScore ranking of the top 100 park systems across the United States, according to the ranking methodologies of the nonpartisan Trust for Public Land. The climate in this area is characterized by hot, humid summers and generally mild to cool winters. According to the Köppen Climate Classification system, Arlington County has a humid subtropical climate, abbreviated "Cfa" on climate maps. As of the 2010 census, there were: The population density was 8,309 people per square mile (2,828/km²), the highest of any county in Virginia. According to the US Census, the racial makeup of the county in 2012 was: There