The September 11, 2001 terrorist attacks occurred at several locations in the United States:

• The Twin Towers of the World Trade Center in Lower Manhattan, New York City, where two hijacked planes (American Airlines Flight 11 and United Airlines Flight 175) were flown into the North and South Towers, causing their collapse

• The Pentagon in Arlington County, Virginia, where American Airlines Flight 77 crashed into the building

• A field near Shanksville, Pennsylvania, where United Airlines Flight 93 crashed after passengers attempted to regain control from hijackers

These sites are now memorialized by the 9/11 Memorial Museum at the World Trade Center site in New York City, the Flight 93 National Memorial in Pennsylvania, and the Pentagon Memorial in Virginia