What major event occurred in the United States on September 11, 2001?

The major event that occurred in the United States on September 11, 2001, was a series of coordinated terrorist attacks carried out by the extremist group al-Qaeda. This day is often referred to simply as "9/11." The attacks involved the hijacking of four commercial airplanes, with two crashing into the Twin Towers of the World Trade Center in New York City, one crashing into the Pentagon in Arlington, Virginia, and the fourth, United Airlines Flight 93, crashing into a field in Pennsylvania after passengers attempted to overcome the hijackers.

This tragic event resulted in the deaths of nearly 3,000 individuals and caused significant destruction. It also led to profound changes in U.S. domestic and foreign policy, including the launch of the War on Terror and increased security measures nationwide. The impact of 9/11 continues to be felt today, shaping aspects of American society and government.

In contrast, the other events listed did not occur on this particular date and are significant in their own right but are unrelated to the September 11 attacks. The stock market crash, while impactful, happened at different times in history. The Cold War's conclusion marked a different era rather than an immediate event on that date. The signing of the Declaration of