Chicago , is a city in the state of Illinois and the largest in the Midwest. With a population of nearly 3 million people located almost entirely in Cook County (a portion of the city's O'Hare International Airport overlaps into DuPage County), Chicago is the third largest city in the United States. The population of Chicago's metropolitan area, which covers several counties (and commonly called Chicagoland), contains over 9.7 million people in Illinois, Wisconsin and Indiana, making it the third largest metropolitan area in the U.S.[1] Chicago has been classified as an alpha world city for its worldwide economic influence.[2]

Chicago was incorporated as a city in 1837. Its location at the site of a portage between the Great Lakes and the Mississippi River watershed aided the city's rapid growth. Today, Chicago is a leading global city and a major transportation hub, as well as the business, financial, and cultural capital of the Midwest.