Four planes. Nineteen hijackers. Two thousand nine hundred ninety seven lives lost. A nation left shattered. It's hard to believe that it's been 15 years since the World Trade Center and Pentagon were hit by hijacked airplanes, since passengers took down an airplane in a Pennsylvania field to foil the terrorists on board. Now, 9/11 is known as the National Day of Service and Remembrance.
Many will do so at 9/11 memorials or quiet services. And some by sharing quotes about a day no American will ever forget. Here are eight moving quotes from that time in our nation's history to help mark this solemn day.