September 11, 2001, was a dark day in United States history. People who wanted to harm the U.S. took control of four airplanes. They flew two planes into skyscrapers in New York City. They crashed one into the Pentagon building, in Washington, D.C. The fourth crashed in Shanksville, Pennsylvania.
This year is the 20th anniversary of the attacks. The nation honored the people who died. Lanterns were lit in Shanksville. In Washington, D.C., 184 benches have been built. That was one for each victim who died there. In New York City, 2,983 names were read aloud. They were the names of all the victims. And two columns of light were beamed into the sky.