Cook County, Illinois

Cook County is the most populous county in the U.S. state of Illinois and the second-most-populous county in the United States, after Los Angeles County, California. More than 40 percent of all residents of Illinois live within Cook County. As of 2020, the population was 5,275,541. The county seat is Chicago, the most populous city in Illinois and the third most populous city in the United States. The county is at the center of the Chicago metropolitan area. Cook County was incorporated in 1831 and named for Daniel Pope Cook, an early Illinois statesman. It achieved its present boundaries in 1839. Within a century, the county recorded explosive population growth, going from a trading post village with a little over six hundred residents to four million, rivaling Paris by the Great Depression. During the first half of the 20th century, it had the absolute majority of Illinois's population. There are more than 800 local governmental units and nearly 130 municipalities located wholly or partially within Cook County, the largest of which is Chicago. The city is home to approximately 54 percent of the entire county's population. The part of the county outside of the Chicago and Evanston city limits is divided into 29 townships; these often divide or share governmental services with local municipalities. Townships within Chicago were abolished in 1902 but are retained for real estate assessment purposes. Evanston Township was formerly coterminous with the City of Evanston but was abolished in 2014. County government is overseen by the Cook County Board of Commissioners, with its president as chief executive, Cook County Clerk and Cook County Treasurer. Countywide state government offices include the Circuit Court of Cook County, the Cook County State's Attorney, the Cook County Sheriff, and the Cook County Assessor. Geographically, the county is the sixth-largest in...