New York is the most populous city in the United States[9] and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world.[10][11][12] New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and entertainment. The home of the United Nations Headquarters,[13] New York is an important center for international affairs and is widely deemed the cultural capital of the world.[14][15][16][17][18] The city is also referred to as New York City or the City of New York[19] to distinguish it from the state of New York, of which it is a part.[20]

The original World Trade Center was a complex with seven buildings featuring landmark twin towers in Lower Manhattan, New York City, United States. The complex opened on April 4, 1973, and was destroyed in 2001 during the September 11 attacks. The site is currently being rebuilt with five new skyscrapers and a memorial to the casualties of the attacks. As of November 2011, only one skyscraper has been completed, with four more expected to be completed before 2020. One World Trade Center will be the lead building for the new complex and is expected to be finished by 2013. A sixth tower is still awaiting confirmation to be built. At the time of their completion, the original 1 and 2 World Trade Center, known colloquially as the Twin Towers, were the tallest buildings in the world.

The September 11 attacks (also referred to as September 11, September 11th or 9/11[nb 1]) were a series of four coordinated suicide attacks upon the United States in New York City and the Washington, D.C. areas on September 11, 2001. On that Tuesday morning, 19 terrorists from the Islamist militant group al-Qaeda hijacked four passenger jets. The hijackers intentionally crashed two planes, American Airlines Flight 11 and United Airlines Flight 175 into the Twin Towers of the World Trade Center in New York City; both towers collapsed within two hours. Hijackers crashed American Airlines Flight 77 into the Pentagon in Arlington, Virginia. The fourth jet, United Airlines Flight 93, crashed into a field near Shanksville, Pennsylvania after passengers attempted to take control before it could reach the hijacker's intended target in Washington, D.C. Nearly 3,000 died in the attacks.

Suspicion quickly fell on al-Qaeda, and in 2004, the group's leader Osama bin Laden, who had initially denied involvement, claimed responsibility for the attacks.[1] 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 for the attacks. 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 law enforcement powers. In May 2011, after years at large, bin Laden was found and killed.

The destruction of the twin towers caused serious damage to the economy of Lower Manhattan and had a significant impact on global markets. Cleanup of the World Trade Center site was completed in May 2002, and the Pentagon was repaired within a year. Numerous memorials were constructed, including the National September 11 Memorial & Museum in New York, the Pentagon Memorial, and the Flight 93 National Memorial in Pennsylvania. Adjacent to the National Memorial, the 1,776 feet (541 m) One World Trade Center is expected to be completed in 2013.