%1

1. September 11

"Nine-Eleven” has become a shorthand reference to the shocking day when four hijacked airliners crashed into the World Trade Center’s twin towers, into a side of the Pentagon and into a field in Pennsylvania—bringing to the U.S. numbing, outrageous examples of the terrorist mayhem that much of the world has experienced in the past. It was a nine-one-one call that shook America’s sense of security.