On September 11, 2001, the United States experienced a series of coordinated terrorist attacks carried out by al-Qaeda, a militant group based in Afghanistan. The attacks involved hijacking four commercial airplanes, two of which crashed into the Twin Towers of the World Trade Center in New York City, one into the Pentagon in Washington, D.C., and one crashed in a field in Shanksville, Pennsylvania, after passengers attempted to regain control of the plane from the hijackers.
The attacks resulted in the deaths of nearly 3,000 people, including passengers and crew members aboard the planes, occupants of the World Trade Center and the Pentagon, and emergency responders who rushed to the scene. It was the deadliest terrorist attack in history and had a profound impact on the United States and the world.