Chicago is the largest city in the state of Illinois, the largest in the Midwest, and, 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), is the third-most populous city in the United States. The Chicago metropolitan area (commonly referred to as Chicagoland) has a population of over 9.7 million people in Illinois, Wisconsin and Indiana, making it also the third largest metropolitan area in the U.S. |