On September 11, 2001, terrorists launched attacks on the World Trade Center in New York and the Pentagon outside Washington, D.C. A fourth hijacked airliner crashed near Shanksville, Pennsylvania. All in all, the acts had killed nearly 3,000 people and changed the nation. Twenty-five years later, the National Museum of the U.S. Army has mounted an exhibit to remember the role played by the Army, and especially the Corps of Engineers, in the response and recovery efforts that followed.