1. The September 11 attacks were a series of four coordinated terrorist attacks by the Islamic terrorist group al-Qaeda on the United States in New York City and the Washington, D.C. metropolitan area on Tuesday, September 11, 2001. The attacks killed 2,996 people and caused at least $10 billion in property and infrastructure damage.
Four passenger airliners were hijacked by 19 al-Qaeda terrorists to be flown into buildings in suicide attacks. Two of the planes were crashed into the North and South towers, respectively, of the World Trade Center complex in New York City. Within two hours, both 110-story towers collapsed with debris and the resulting fires causing partial or complete collapse of all other buildings in the WTC complex, including the 47-story 7 World Trade Center tower, as well as significant damage to ten other large surrounding structures. A third plane was crashed into the Pentagon (the headquarters of the United States Department of Defense), leading to a partial collapse in its western side. The fourth plane was targeted at Washington but crashed into a field near Shanksville, Pennsylvania after its passengers tried to overcome the hijackers. In total, 2,996 people died in the attacks, including the 227 civilians and 19 hijackers aboard the four planes. It was the deadliest incident for firefighters and law enforcement officers in the history of the United States, with 343 and 72 killed respectively.
The United States responded by launching the War on Terror and invading Afghanistan to depose the Taliban, which had harbored al-Qaeda. Many countries strengthened their anti-terrorism legislation and expanded law enforcement powers. Having evaded capture for almost a decade, bin Laden was located and killed by U.S. forces in May 2011.
Numerous memorials have been constructed, including the National September 11 Memorial & Museum in New York, the Pentagon Memorial, and the Flight 93 National Memorial in