Chicago is the largest city in the US state of Illinois and the third most populous city in the United States, with around 2.7 million residents. Its metropolitan area, sometimes called "Chicagoland," is the third largest in the United States, with an estimated 9.8 million people within its metropolitan area.
Chicago was incorporated as a town in 1837, near a portage between the Great Lakes and the Mississippi River watershed. Today, the city retains its status as a major hub for industry, telecommunications and infrastructure, with O'Hare International Airport being the second busiest airport in the world in terms of traffic movements. In 2008, the city hosted 45.6 million domestic and overseas visitors. Among metropolitan areas, the Chicago area has the 4th largest Gross Domestic Product (GDP) in the world. Chicago is one of the most important Worldwide Centres of Commerce and trade.
The city's notoriety has found expression in numerous forms of popular culture, including novels, plays, movies, songs, various types of journals (for example, sports, entertainment, business, trade, and academic), and the news media. Chicago has many nicknames, which reflect the impressions and opinions about historical and contemporary Chicago. The best known include: "Chi-town," "Windy City," "Second City," and the "City of Big Shoulders."
The culture of Chicago is particularly known for various forms of performing arts, such as improvisational comedy, and music, such as Chicago blues and soul. The city continues to cultivate a strong classical music, popular music, dance and performing arts tradition, rooted in Western civilization, as well as other traditions carried forward by its American, African, Asian, European, and Hispanic citizens. Chicago is known for a robust and vigorous tradition of surrealist, funky figurative paintings and art, such as the famous Chicago Imagist group. The city is additionally known for various popular culinary dishes, notably the deep-dish pizza, the Chicago-style hot dog and the Chicago-style Italian beef sandwich.