File:Flag From Ground Zero.jpg

English: The September 11, 2001 terrorist attacks were the most lethal terrorist attack in history, taking the lives of 3,000 Americans and international citizens and ultimately leading to far-reaching changes in anti-terror approaches and operation in the U.S. and around the globe. Galvanized by the unprecedented terrorist attack, the FBI responded in an unprecedented fashion. In addition to assisting emergency response efforts, the FBI began its PENTTBOM investigation, short for Pennsylvania, Pentagon, and Twin Towers Bombing. The PENTTBOM investigation was the largest investigation ever conducted by the FBI. Thousands of agents across the nation interviewed witnesses and sources; they followed more than half-a-million investigative leads worldwide, including several thousand tips from the public, in order to determine what had happened, who did it, and how future acts could be prevented. At the peak of the case, more than half of the Bureau’s agents worked with other agencies to identify the hijackers and their sponsors. Within hours, the FBI was able to start identifying the 19 terrorists responsible. A case was also built against Zacarias Moussaoui, who pleaded guilty in 2005 to six charges related to his participation in the 9/11 conspiracy. This artifact is the American flag from Ground Zero in New York City.