Chicago (/ʃɨˈkɑːɡoʊ/ or /ʃɨˈkɔːɡoʊ/) is the third most populous city in the United States. With over 2.7 million residents, it is the most populous city in the state of Illinois and the Midwest. The Chicago metropolitan area, often referred to as Chicagoland, is home to nearly 10 million people and is the third-largest in the United States. Chicago is the seat of Cook County.
Chicago was incorporated as a city in 1837, near a portage between the Great Lakes and the Mississippi River watershed, and experienced rapid growth in the mid-nineteenth century. Today, the city is an international hub for finance, commerce, industry, technology, telecommunications, and transportation, with O'Hare International Airport being the busiest airport in the world; it also has the largest number of U.S. highways and railroad freight. In 2012, Chicago was listed as an alpha global city by the Globalization and World Cities Research Network, and ranks seventh in the world in the 2014 Global Cities Index. As of 2012, Chicago had the third largest gross metropolitan product in the United States at US$571 billion.
In 2014, Chicago hosted 50.2 million international and domestic visitors. Chicago's culture includes contributions to the visual arts, novels, film, theater, especially improvisational comedy, and music, particularly jazz, blues, soul, and house music. The city has many nicknames, which reflect the impressions and opinions about historical and contemporary Chicago. The best-known include the "Windy City" and "Second City". Chicago has professional sports teams in each of the major professional leagues.