Cook County, Illinois, USA

Cook County is a county in northeastern Illinois along the southwestern shore of Lake Michigan, with Chicago serving as its county seat and dominant population, economic and transportation center. The county extends from Chicago’s dense urban core into northern, western and southern suburbs and includes more than 130 municipalities, as well as several unincorporated areas. Its landscape includes the Lake Michigan shoreline, the Chicago and Des Plaines river systems, extensive transportation and industrial corridors, and large tracts of protected land managed by the Forest Preserves of Cook County. Cook County covers approximately 945 square miles of land, had about 5.28 million residents at the 2020 census and is the most populous county in Illinois and the second-most populous county in the United States.