Cook County

Cook County is an administrative unit in northeastern Illinois, stretching from the shore of Lake Michigan to the western suburbs. Chicago sits in the eastern portion of this territory and serves as the seat.

The county was established in mid-January 1831 and named after Daniel Pope Cook, an early Illinois politician. Over the following decades, this territory grew into a major commercial hub of the Midwest.

The population of 5.2 million inhabitants represents numerous ethnic communities, with substantial White, African American, and Hispanic populations forming distinct neighborhoods.

Access to county government and public services is available across dozens of towns and neighborhoods spread throughout the territory. Main buildings are located in downtown Chicago, where offices and courts operate.

The county court system ranks among the largest single judicial authorities in the country, processing hundreds of cases every day. Within this court complex sits one of the largest single-building detention centers in the United States.

Location: Illinois

Inception: January 15, 1831

Capital city: Chicago

Elevation above the sea: 950 m

Shares border with: McHenry County, Lake County, Will County, DuPage County, Kane County, Porter County, Berrien County

Website: https://cookcountyil.gov

GPS coordinates: 41.80000,-87.71667

Latest update: December 15, 2025 03:22