On September 11 , 2001 , al-Qaeda terrorists hijacked four commercial airliners and attacked the World Trade Center and the Pentagon in the September 11 attacks , killing nearly 3,000 and injuring over 6,000 people . Osama bin Laden claimed responsibility for the attacks . President Bush ordered all flights grounded and U.S. airspace remained closed for the rest of the week . An emergency bailout package for the airline industry was passed , and stocks fell dramatically when markets re-opened the following week . In response to the attacks , the Bush administration and Congress passed the controversial USA PATRIOT Act , aimed at enhancing security , and established the Department of Homeland Security , a mass consolidation of many federal agencies charged with investigation , intelligence , and emergency management . A new Terrorist Finance Tracking Program monitored the movements of terrorists ' financial resources but was discontinued after being revealed by '' The New York Times '' . Telecommunication usage by known and suspected terrorists was studied through the NSA electronic surveillance program . On October 7 , 2001 , the United States invaded Afghanistan as part of a global War on Terrorism , aimed at rooting out al-Qaeda , the Taliban , and other terrorist organizations
September 11 attacks
September 11 attacks
History of the United States (1991–2008)