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

On September 11, 2001, a series of coordinated terrorist attacks were carried out by the extremist group al-Qaeda against the United States. The most notable events of that day involved the hijacking of four commercial airliners. Two planes were flown into the Twin Towers of the World Trade Center in New York City, leading to their collapse. A third plane struck the Pentagon, while the fourth, United Airlines Flight 93, crashed into a field in Pennsylvania after passengers attempted to overcome the hijackers. This tragic event resulted in the loss of thousands of lives and significantly impacted U.S. domestic and foreign policy, leading to increased security measures and the initiation of the War on Terror.

The other options do not accurately reflect significant events on that date. The stock market crash happened on different occasions, with notable crashes in the 1929 and 1987. The moon landing occurred in 1969, marking humanity's first voyage to the Moon. The first presidential election took place in 1788-1789, long before September 11, 2001. Thus, the events described in the other options are either historically inaccurate for that date or refer to events that occurred in completely different contexts.