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 on the United States on the morning of Tuesday, September 11, 2001. The attacks consisted of suicide attacks used to target symbolic U.S. landmarks.

Four passenger airliners—which all departed from airports on the U.S. East Coast bound for California—were hijacked by 19 al-Qaeda terrorists to be flown into buildings. Two of the planes, American Airlines Flight 11 and United Airlines Flight 175, were crashed into the North and South towers, respectively, of the World Trade Center complex in New York City. Within an hour and 42 minutes, both 110-story towers collapsed with debris and the resulting fires causing partial or complete collapse of all other buildings in the World Trade Center complex, including the 47-story 7 World Trade Center tower, as well as significant damage to ten other large surrounding structures. A third plane, American Airlines Flight 77, was crashed into the Pentagon (the headquarters of the United States Department of Defense) in Arlington County, Virginia, leading to a partial collapse in the Pentagon’s western side. The fourth plane, United Airlines Flight 93, initially was steered toward Washington, D.C., but crashed into a field near Shanksville, Pennsylvania, after its passengers tried to overcome the hijackers. In total, the attacks claimed the lives of 2,996 people (including the 19 hijackers) and caused at least $10 billion in property and infrastructure damage. It was the deadliest incident for firefighters and law enforcement officers[4] in the history of the United States, with 343 and 72 killed respectively.

Suspicion for the attack quickly fell on al-Qaeda. The United States responded to the attacks 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 the powers of law enforcement and intelligence agencies to prevent terrorist attacks. Although al-Qaeda’s leader, Osama bin Laden, initially denied any involvement, in 2004, he claimed responsibility for the attacks. Al-Qaeda and bin Laden cited U.S. support of Israel, the presence of U.S. troops in Saudi Arabia, and sanctions against Iraq as motives. Having evaded capture for almost a decade, bin Laden was located and killed by members of the U.S. military in May 2011.

The destruction of the World Trade Center and nearby infrastructure caused serious damage to the economy of Lower Manhattan and had a significant effect on global markets, closing Wall Street until September 17 and the civilian airspace in the U.S. and Canada until September 13. Many closings, evacuations, and cancellations followed, out of respect or fear of further attacks. Cleanup of the World Trade Center site was completed in May 2002, and the Pentagon was repaired within a year. On November 18, 2006, construction of One World Trade Center began at the World Trade Center site. The building was officially opened on November 3, 2014. Numerous memorials have been constructed, including the National September 11 Memorial & Museum in New York City, the Pentagon Memorial in Arlington County, and the Flight 93 National Memorial in a field near Shanksville.

Casualties

The attacks resulted in the deaths of 2,996 people, including the 19 hijackers. The 2,977 victims included 246 on the four planes (from which there were no survivors), 2,606 in the World Trade Center and in the surrounding area, and 125 at the Pentagon. Nearly all of those who perished were civilians with the exceptions of 72 law enforcement officers, 343 firefighters, and 55 military personnel who died in the attacks. After New York, New Jersey lost the most state citizens, with the city of Hoboken having the most citizens that died in the attacks. More than 90 countries lost citizens in the September 11 attacks. The attacks of September 11, 2001, marked it the worst terrorist attack in world history and the deadliest foreign act of destruction to life and property on American soil since the Japanese surprise attack on Pearl Harbor on December 7, 1941.

In Arlington County, 125 Pentagon workers lost their lives when Flight 77 crashed into the western side of the building. Of these, 70 were civilians and 55 were military personnel, many of them who worked for the United States Army or the United States Navy. The Army lost 47 civilian employees, six civilian contractors, and 22 soldiers, while the Navy lost six civilian employees, three civilian contractors, and 33 sailors. Seven Defense Intelligence Agency (DIA) civilian employees were also among the dead in the attack, as well as an Office of the Secretary of Defense (OSD) contractor Lieutenant General Timothy Maude, an Army Deputy Chief of Staff, was the highest-ranking military official killed at the Pentagon.

In New York City, more than 90% of the workers and visitors who died in the towers had been at or above the points of impact. In the North Tower, 1,355 people at or above the point of impact were trapped and died of smoke inhalation, fell or jumped from the tower to escape the smoke and flames, or were killed in the building’s eventual collapse. The destruction of all three staircases in the tower when Flight 11 hit made it impossible for anyone above the impact zone to escape. 107 people below the point of impact died as well.

In the South Tower, one stairwell, Stairwell A, was left intact after Flight 175 hit, allowing 14 people located on the floors of impact (including one man who saw the plane coming at him) and four more from the floors above to escape. 911 operators who received calls from individuals inside the tower were not well informed of the situation as it rapidly unfolded and as a result, told callers not to descend the tower on their own. 630 people died in that tower, fewer than half the number killed in the North Tower.

Casualties in the South Tower were significantly reduced by some occupants deciding to start evacuating as soon as the North Tower was struck.

At least 200 people fell or jumped to their deaths from the burning towers (as exemplified in the photograph The Falling Man), landing on the streets and rooftops of adjacent buildings hundreds of feet below.[119] Some occupants of each tower above the point of impact made their way toward the roof in hope of helicopter rescue, but the roof access doors were locked. No plan existed for helicopter rescues, and the combination of roof equipment and thick smoke and intense heat prevented helicopters from approaching. A total of 411 emergency workers died as they tried to rescue people and fight fires. The New York City Fire Department (FDNY) lost 343 firefighters, including a chaplain, two paramedics, and a fire marshal. The New York City Police Department (NYPD) lost 23 officers. The Port Authority Police Department (PAPD) lost 37 officers. Eight emergency medical technicians (EMTs) and paramedics from private emergency medical services units were killed.

Cantor Fitzgerald L.P., an investment bank on the 101st–105th floors of the North Tower, lost 658 employees, considerably more than any other employer. Marsh Inc., locatedimmediately below Cantor Fitzgerald on floors 93–100, lost 358 employees, and 175 employees of Aon Corporation were also killed. The National Institute of Standards and Technology (NIST) estimated that about 17,400 civilians were in the World Trade Center complex at the time of the attacks. Turnstile counts from the Port Authority suggest 14,154 people were typically in the Twin Towers by 8:45 a.m. The vast majority of people below the impact zone safely evacuated the buildings.

Weeks after the attack, the death toll was estimated to be over 6,000, more than twice the number of deaths eventually confirmed.[138] The city was only able to identify remains for about 1,600 of the World Trade Center victims. The medical examiner’s office collected “about 10,000 unidentified bone and tissue fragments that cannot be matched to the list of the dead”. Bone fragments were still being found in 2006 by workers who were preparing to demolish the damaged Deutsche Bank Building. In 2010, a team of anthropologists and archaeologists searched for human remains and personal items at the Fresh Kills Landfill, where seventy-two more human remains were recovered, bringing the total found to 1,845. DNA profiling continues in an attempt to identify additional victims. The remains are being held in storage in Memorial Park, outside the New York City Medical Examiner’s facilities. It was expected that the remains would be moved in 2013 to a repository behind a wall at the 9/11 museum. In July 2011, a team of scientists at the Office of Chief Medical Examiner was still trying to identify remains, in the hope that improved technology will allow them to identify other victims. On March 20, 2015, the 1,640th victim was identified.

There are still 1,113 victims who have not been identified.

Damage

Along with the 110-floor Twin Towers, numerous other buildings at the World Trade Center site were destroyed or badly damaged, including WTC buildings 3 through 7 and St. Nicholas Greek Orthodox Church. The North Tower, South Tower, the Marriott Hotel (3 WTC), and 7 WTC were completely destroyed. The U.S. Customs House (6 World Trade Center), 4 World Trade Center, 5 World Trade Center, and both pedestrian bridges connecting buildings were severely damaged. The Deutsche Bank Building on 130 Liberty Street was partially damaged and demolished some years later, starting in 2007. The two buildings of the World Financial Center also suffered damage.

The Deutsche Bank Building across Liberty Street from the World Trade Center complex was later condemned as uninhabitable because of toxic conditions inside the office tower, and was deconstructed.The Borough of Manhattan Community College’s Fiterman Hall at 30 West Broadway was condemned due to extensive damage in the attacks, and is being rebuilt. Other neighboring buildings (including 90 West Street and the Verizon Building) suffered major damage but have been restored. World Financial Center buildings, One Liberty Plaza, the Millenium Hilton, and 90 Church Street had moderate damage and have since been restored. Communications equipment on top of the North Tower was also destroyed, but media stations were quickly able to reroute the signals and resume their broadcasts.

The Pentagon was severely damaged by the impact of American Airlines Flight 77 and ensuing fires, causing one section of the building to collapse. As the airplane approached the Pentagon, its wings knocked down light poles and its right engine hit a power generator before crashing into the western side of the building. The plane hit the Pentagon at the first-floor level. The front part of the fuselage disintegrated on impact, while the mid and tail sections kept moving for another fraction of a second. Debris from the tail section penetrated furthest into the building, breaking through 310 feet (94 m) of the three outermost of the building’s five rings.

National September 11 Memorial & Museum

The National September 11 Memorial & Museum (known separately as the 9/11 Memorial and 9/11 Memorial Museum) is the principal memorial and museum, respectively, commemorating the September 11 attacks of 2001 and the World Trade Center bombing.

The memorial is located at the World Trade Center site, the former location of the Twin Towers (which were destroyed during the September 11 attacks). It is operated by a non-profit corporation, headed by Joe Daniels, whose mission is to raise funds for, program, own and operate the memorial and museum at the World Trade Center site.

A memorial was planned in the immediate aftermath of the attacks and destruction of the World Trade Center for the victims including those involved in rescue operations.The winner of the World Trade Center Site Memorial Competition was Israeli architect Michael Arad of Handel Architects, a New York- and San Francisco-based firm. Arad worked with landscape-architecture firm Peter Walker and Partners on the design, a forest of trees with two square pools in the center where the Twin Towers stood. In August 2006, the World Trade Center Memorial Foundation and the Port Authority of New York and New Jersey began heavy construction on the memorial and museum. The design is consistent with the original Daniel Libeskind master plan, which called for the memorial to be 30 feet (9.1 m) below street level—originally 70 feet (21 m)—in a plaza, and was the only finalist to disregard Libeskind’s requirement that the buildings overhang the footprints. The World Trade Center Memorial Foundation was renamed the National September 11 Memorial & Museum in 2007.

On September 11, 2011, a dedication ceremony commemorating the tenth anniversary of the attacks was held at the memorial. It opened to the public the following day; the museum was dedicated on May 15, 2014 and opened on May 21. Three months after its opening, the memorial had been visited by over a million people.

In 2012 Tuesday’s Children, a non-profit family-service organization dedicated to individuals directly impacted by 9/11 and those who have lost loved ones to terrorism worldwide, joined with the 9/11 Memorial to offer private tours to family members of
9/11 victims and first responders.