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Two special rays of light will shine above New York City on September 11. They will help Americans remember a sad event.

On September 11, 2001, terrorists attacked the U.S. They took control of four airplanes by force. Two of the planes destroyed the two tallest buildings in New York City, the Twin Towers of the World Trade Center. Another plane struck the Pentagon, a military building in Virginia. The fourth one crashed in a field in Pennsylvania. Sadly, thousands of people died.

Since then, the U.S. has caught many of the people who planned the attacks. And each year, the two lights shine to honor those who died on September 11.