A visual timeline of how the events unfolded in the U.S. on September 11, 2001, when terrorists hijacked planes and crashed them into key buildings, including the Twin Towers of the World Trade Center in New York. Over 3,000 people were killed in the deadliest attack on the U.S.

After 25 years, 100 million Americans have no memory of the day that changed everything. In an age of social media, disinformation and mistrust, that can be dangerous.

Two of the hijacked planes struck the Twin Towers in New York and a third crashed into the Pentagon. | World News

The 2001 attacks unfolded across New York, Virginia, and Pennsylvania, killing nearly 3,000 people and permanently changing American life.