Monday marks 22 years since September 11, 2001, when terrorists attacked New York City and the United States, claiming thousands of lives.

The 9/11 attacks left 2,977 dead across New York, Washington, D.C. and Pennsylvania, according to the 9/11 Memorial and Museum. That total includes the 2,753 who died after the planes struck the Twin Towers, 184 people at the Pentagon and 40 people who died when Flight 93 crash-landed in Pennsylvania.

The youngest flight passenger who died was Christine Hanson, a 2-year-old on her way to Disneyland on United Airlines Flight 175. The oldest was Robert Norton, 82, who was on American Airlines Flight 11.

343 firefighters died on 9/11, which at the time was nearly half the number of on-duty deaths in the New York City Fire Department’s entire 100-year history.