PHOTOS: Remembering 9/11 - ABC News

Nearly 3,000 people died on the day of a series of coordinated attacks against the United States by terrorists who hijacked four passenger jets that crashed into the World Trade Center buildings in New York, the Pentagon and a field in rural Pennsylvania.

Smoke rises from the World Trade Center in the Manhattan borough of New York after the terror attack on Sept. 11, 2001.

Warning: This slideshow contains images that some may find disturbing. Viewer discretion is advised.