On September 11, 2001, terrorists attacked the United States. Terrorists captured four American passenger airplanes. They used the planes as weapons. Two planes hit the World Trade Center in New York City. One plane hit the Pentagon, a government building in Virginia. The last plane crashed in Pennsylvania. The attacks killed almost 3,000 people. After the terrorist attacks on September 11, 2001, the U.S. began the war on terrorism.
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