Twenty-four years ago, the United States experienced the worst foreign terror attack on national soil in its history, when Islamic extremists launched four coordinated airplane hijackings that killed thousands.
Nearly 3,000 Americans were killed in the attacks on Sept. 11, 2001. Airplanes crashed into both Twin Towers in New York City and the Pentagon outside of Washington, D.C. Another plane crashed in a field in rural Pennsylvania after the passengers revolted.
The attacks inspired many changes at the social, political and international level, such as the U.S. launching a global war on terrorism that saw troops deployed to Iraq and Afghanistan.
Yet, even as American troops have returned home, mastermind Osama bin Laden has been killed and parts of the PATRIOT Act have expired, many developments spawned from that historic day remain.
The following pages highlight five ongoing stories stemming from the 9/11 tragedy.