September 11

The September 11 attacks (often referred to as 9/11) were a series of coordinated suicide attacks by Islamic extremists belonging to the al-Qaeda movement upon the United States on September 11, 2001. On that morning, terrorists affiliated with al-Qaeda hijacked four commercial passenger jet airliners.^[1]^[2] The hijackers intentionally crashed two of the airliners into the Twin Towers of the World Trade Center in New York City, killing everyone on board and many others working in the building, causing both buildings to collapse within two hours, destroying at least two nearby buildings and damaging others. The hijackers crashed a third airliner into the Pentagon. The fourth plane crashed into a field near Shanksville in rural Somerset County, Pennsylvania, after some of its passengers and flight crew attempted to retake control of the plane, which the hijackers had redirected toward Washington, D.C. There are no known survivors from any of the flights.

Excluding the 19 hijackers, 2,974 people died in the attacks. Another 24 are missing and presumed dead. The overwhelming majority of casualties were civilians, including nationals of over 90 different countries. In addition, the death of at least one person from lung disease was ruled by a medical examiner to be a result of exposure to dust from the World Trade Center's collapse, as rescue and recovery workers were exposed to airborne contaminants following the buildings' collapse.

The United States responded to the attacks by declaring a War on Terrorism, launching an invasion of Afghanistan to depose the Taliban, who had harbored al-Qaeda terrorists, and enacting the USA PATRIOT Act. Many other nations also strengthened their anti-terrorism legislation and expanded law enforcement powers. Stock exchanges closed for almost a week, and posted enormous losses upon reopening, especially in the airline and insurance industries. The economy of Lower Manhattan ground to a halt, as billions of dollars in office space was damaged or destroyed.

The damage to the Pentagon was cleared and repaired within a year, and a small memorial was built on the site. Rebuilding the World Trade Center site has proven more difficult, with controversy over possible designs as well as the pace of construction. Construction delays, revised cost estimates, security concerns, and public criticism have all lead to significant changes and delays to the final plans in rebuilding the complex.