Chicago is the largest city in the state of Illinois and the largest in the Midwest. With a population of nearly 3 million people, the city is the third largest in the United States. It is the anchor of the Chicago metropolitan area, commonly called Chicagoland, which has a population of over 9.7 million people in Illinois, Wisconsin and Indiana, making it the third largest metropolitan area in the U.S. Rich in history and renowned for its architecture, the city is classified as an alpha world city. The City of Chicago is almost entirely located in Cook County, Illinois, with a small portion overlapping into DuPage County, while the metropolitan area extends over several counties.
Located at the site of a portage between the Great Lakes and the Mississippi River watershed, Chicago was incorporated as a city in 1837. It rapidly became a major transportation hub, as well as the business, financial, and cultural capital of the Midwest. Since the Chicago World's Fair of 1893, it has been regarded as one of the ten most influential cities in the world.
City of Chicago Website