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What Happened on September 11, 2001

On the morning of September 11, 2001, 19 terrorists affiliated with al-Qaeda hijacked four commercial airliners. Two were flown into the North and South Towers of the World Trade Center in New York City, causing both towers to collapse within about two hours. A third plane struck the Pentagon in Arlington, Virginia. The fourth, United Airlines Flight 93, crashed in a field near Shanksville, Pennsylvania, after passengers and crew attempted to retake control of the aircraft from the hijackers.

How Many People Died

According to the National September 11 Memorial & Museum, 2,977 people were killed across all four locations, not including the 19 hijackers. Thousands more were injured, and in the years since, additional deaths have been linked to illnesses caused by exposure to toxic dust and debris at Ground Zero — a toll that continues to grow through the federally funded World Trade Center Health Program.

What Changed Afterward

The attacks reshaped U.S. policy in ways still felt today. Congress passed the USA PATRIOT Act weeks later, expanding government surveillance powers. The Department of Homeland Security was created in 2002 and became operational in 2003, consolidating 22 federal agencies. Air travel changed permanently with the creation of the Transportation Security Administration (TSA). The attacks also led directly to the U.S. invasion of Afghanistan later in 2001 and shaped two decades of American foreign policy known broadly as the War on Terror.

How the Date Is Marked Today

September 11 is observed in the United States as Patriot Day, a national day of service and remembrance. Ceremonies are held each year at the National September 11 Memorial & Museum in New York, the Pentagon Memorial in Arlington, and the Flight 93 National Memorial in Shanksville, Pennsylvania — each built at the exact site of one of the four crashes.

If This Anniversary Is Hard for You

For survivors, first responders, and families who lost someone, this date can bring up real grief even decades later — that's a completely normal response to a genuinely traumatic event, not something to push past on your own. The Disaster Distress Helpline (1-800-985-5990) offers free, confidential support year-round, including around difficult anniversaries like this one.