New York City (pronounced /nʲuːˈjɔɹk/) (officially The City of New York) is the most populous city in the United States, with its metropolitan area ranking among the largest urban areas in the world. For more than a century, it has been one of the world's major centers of commerce and finance. New York City is rated as an alpha world city for its global influences in media, politics, education, entertainment and fashion. The city's cultural centers for arts are among the nation's most influential. The city is a major center for foreign affairs, hosting the headquarters of the United Nations. Residents of the city are known as New Yorkers. The current mayor of New York City is Michael Bloomberg.New York City comprises five boroughs, each of which is coextensive with a county: The Bronx, Brooklyn, Manhattan, Queens and Staten Island. With over 8.2 million residents within an area of 322 square miles (830 km²), New York City is the most densely populated major city in the United States.Many of the city's neighborhoods and landmarks are known around the world. The Statue of Liberty greeted millions of immigrants as they came to America in the late 19th and early 20th centuries, at Ellis Island, a small part of which lies within the city. Wall Street, in Lower Manhattan, has been a dominant global financial center since World War II and is home to the New York Stock Exchange. The city has been home to several of the tallest buildings in the world, including the Empire State Building and the twin towers of the World Trade Center, which were destroyed in the September 11, 2001 attacks.New York is the birthplace of many American cultural movements, including the Harlem Renaissance in literature and visual art, abstract expressionism (also known as the New York School) in painting, and hip hop, punk, salsa, and Tin Pan Alley in music. In 2005, nearly 170 languages were spoken in the city and 36% of its population was born outside the United States. With its 24-hour subway and constant bustling of traffic and people, New York is known as "The City That Never Sleeps;" it was first linked with "Gotham" by Washington Irving in 1807.