What significant event took place in the United States on September 11, 2001?

The significant event that took place in the United States on September 11, 2001, was a series of coordinated terrorist attacks carried out by the extremist group al-Qaeda. On that day, terrorists hijacked four commercial airplanes, crashing two of them into the Twin Towers of the World Trade Center in New York City and another into the Pentagon in Arlington, Virginia. The fourth plane, United Airlines Flight 93, was headed toward another target in Washington, D.C. but crashed in Pennsylvania after passengers attempted to regain control from the hijackers.

This tragic event resulted in the deaths of nearly 3,000 people and had profound and lasting effects on national security policies, U.S. foreign policy, and the global landscape in terms of counter-terrorism efforts. The aftermath led to the implementation of the USA PATRIOT Act, the establishment of the Department of Homeland Security, and wars in Afghanistan and Iraq. The attacks are widely referred to as 9/11 and are commemorated each year in remembrance of the lives lost and the impact on both the U.S. and the world.

The other options refer to events that did not occur on that date. Peace accords, presidential inaugurations, and moon landings are significant historical events