Cook County, Illinois

Cook County
Official seal of Cook County
Location within Illinois
Location within Illinois
Illinois' location within the United States
Illinois' location within the United States
Coordinates: 41°48′31″N 87°53′20″W / 41.80861°N 87.88889°W / 41.80861; -87.88889
CountryUnited States
StateIllinois
RegionNorthern Illinois
Metro areaChicago metropolitan area
IncorporatedJanuary 15, 1831; 193 years ago (1831-01-15)
Named forDaniel Pope Cook
County seatChicago
Incorporated municipalities
135 (total)
  • 23 cities, 1 town, 111 villages
  • (located entirely or partially
    within county boundaries)
Government
 • TypeCounty commission
 • BodyBoard of Commissioners
 • PresidentToni R. Preckwinkle (D)
Area
 • County
1,635 sq mi (4,230 km2)
 • Land945 sq mi (2,450 km2)
 • Water690 sq mi (1,800 km2)
 • Metro
10,874 sq mi (28,160 km2)
 • Rank6th largest county in Illinois
Highest elevation950 ft (290 m)
Lowest elevation580 ft (180 m)
Population
 (2020)
 • County
5,275,541
 • Estimate 
(2023)
5,087,072 Decrease
 • Density3,200/sq mi (1,200/km2)
GDP
 • County$485.547 billion (2022)
Time zoneUTC−6 (Central)
 • Summer (DST)UTC−5 (Central)
ZIP Code prefixes
600xx–608xx
Area codes847/224, 312/872, 773/872, 708/464
FIPS code17-031
GNIS feature ID1784766
Congressional districts1st, 2nd, 3rd, 4th, 5th, 6th, 7th, 8th, 9th, 10th, 11th
Websitewww.cookcountyil.gov

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.[5] 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, 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 Illinois by land area and the largest by total area. It shares the state's Lake Michigan shoreline with Lake County. Including its lake area, Cook County has a total area of 1,635 square miles (4,234.6 km2), the largest county in Illinois, of which 945 square miles (2,447.5 km2) is land and 690 square miles (1,787.1 km2) (42.16%) is water. Land-use in Cook County is mostly urban and densely populated. Within Cook County, the state of Illinois took advantage of its Lake Michigan access and the Chicago Portage, beginning with the construction of the Illinois and Michigan Canal in 1848. This helped make the region a central transit hub for the nation. Chicago, with its location on the Great Lakes and via the St. Lawrence Seaway, is a global port city, giving Cook County an international shipping port.

Cook County's population is larger than that of 28 U.S. states and territories, and larger than the population of 11 of the 13 Canadian provinces and territories.[6] Cook County is at the center of the Chicago metropolitan area, which has a population of approximately 10 million people.

  1. ^ a b "Lowest and Highest Points in Cook County". Illinois State Geological Survey. Archived from the original on December 1, 2016. Retrieved November 30, 2016. Greater than 950 ft max and Less than 580 ft min
  2. ^ Streamwood Quadrangle – Illinois – Cook Co (Map). 1:24,000. 7.5-Minute Series (Topographic). United States Geological Survey. 2013.
  3. ^ Chicago Loop Quadrangle – Illinois – Cook Co (Map). 1:24,000. 7.5-Minute Series (Topographic). United States Geological Survey. 2013.
  4. ^ "Gross Domestic Product: All Industries in Cook County, IL". fred.stlouisfed.org.
  5. ^ "About Cook County | CookCountyIL.gov". www.cookcountyil.gov. Archived from the original on November 30, 2020. Retrieved November 15, 2020.
  6. ^ "County Population Estimates". Archived from the original on September 24, 2015. Retrieved April 4, 2014.