On September 11, 2001, terrorists hijacked four jets and used them as weapons in attacks against the United States. They flew two of the planes into the Twin Towers of the World Trade Center in New York City. (Click here for a close-up map of New York City attacks.) They crashed a third plane into the Pentagon, which houses the Department of Defense, near Washington, D.C. (Click here for a close-up map of D.C. attacks.) The fourth plane crashed in a field in Shanksville, Pennsylvania. Officials believe that the terrorists intended to destroy either the White House or the U.S. Capitol with that plane. Passengers on the plane fought the terrorists and prevented them from reaching their goal.