The September 11 attacks, also referred to as 9/11, were a series of four coordinated terrorist attacks by the Islamic terrorist group al-Qaeda against the United States on the morning of Tuesday, September 11, 2001.
The attacks killed 2,996 people, injured over 6,000 others, and caused at least $10 billion in infrastructure and property damage.
Additional people died of 9/11-related cancer and respiratory diseases in the months and years following the attacks.
9/11 is the single deadliest incident for firefighters and law enforcement officers in the history of the United States, with 343 and 72 killed, respectively.