Final answer:
September 11 is observed in remembrance of the terrorist attacks in 2001, when nearly 3,000 people died after hijacked planes struck the World Trade Center and other locations. It is a time to honor the heroism of emergency workers and the unity shown by Americans post-tragedy.
Step-by-step explanation:
On the morning of September 11, 2001, a series of terrorist attacks forever transformed the United States and the world. Nineteen terrorists associated with the extremist group al-Qaeda hijacked four commercial airplanes. Two of these planes were flown into the iconic Twin Towers of the World Trade Center in New York City, causing both to collapse and resulting in widespread death and destruction. This day is solemnly remembered for the loss of nearly 3,000 innocent lives, including 400 emergency workers, and is marked by commemorations honoring the heroism displayed by the first responders and ordinary citizens.
The aftermath of the attacks sparked global condemnation and profound sympathy towards the victims. It raised questions about the United States' role in the world, privacy versus security, the meaning of American identity, and the cost of liberty. The altruistic response of the American people, including the surge in patriotic sentiment, charitable contributions, and increased enlistments in the military, demonstrated resilience and unity in the face of terrorism.