2001 (September 11) Almost 3,000 are killed in the September 11, 2001 attacks at the World Trade Center in New York City, The Pentagon in Arlington, Virginia, and in rural Shanksville, Pennsylvania after American Airlines Flight 11 and United Airlines Flight 175 crash into the World Trade Center's Twin Towers in New York City, American Airlines Flight 77 crashes into the Pentagon, and United Airlines Flight 93 crashes into a grassland in Pennsylvania.