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. 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 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 , the largest county in Illinois, of which is land and (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. The county is at the center of the Chicago metropolitan area, which has a population of approximately 10 million people.
History Cook County was created on January 15, 1831, out of Putnam County by an act of the Illinois General Assembly. It was the 54th county established in Illinois and was named after Daniel Pope Cook. As a politician, lawyer and newspaper publisher from the U.S. state of Illinois as well as an anti-slavery advocate, Cook became one of the earliest and youngest statesmen in Illinois history. He served as the second U.S. representative from Illinois and the state's first attorney general. In 1839, DuPage County was carved out of Cook County.
The shape of Cook County and the neighboring counties has remained the same since DuPage County was formed. The population in each county and the split of agriculture compared to residential and industrial activity has changed dramatically over the intervening decades to 2020. The county began with 10,201 people in the census of 1840, growing rapidly to 5,150,233 people estimated for 2019 by the US census. Growth was rapid in the 19th century, with the County reaching 2.4 million people by 1910. In the 20th century, the County reached 5.1 million population.
Cook County is nearly completely developed, with little agricultural land remaining near the outer county boundaries.
Demographics
2020 census
As of the 2020 census, the county had a population of 5,275,541. The median age was 37.4 years. 20.9% of residents were under the age of 18 and 15.1% of residents were 65 years of age or older. For every 100 females there were 94.0 males, and for every 100 females age 18 and over there were 91.5 males age 18 and over.
The racial makeup of the county was 44.5% White, 22.9% Black or African American, 1.1% American Indian and Alaska Native, 7.8% Asian, <0.1% Native Hawaiian and Pacific Islander, 13.4% from some other race, and 10.4% from two or more races. Hispanic or Latino residents of any race comprised 26.2% of the population.
99.9% of residents lived in urban areas, while 0.1% lived in rural areas.
There were 2,086,940 households in the county, of which 28.4% had children under the age of 18 living in them. Of all households, 38.5% were married-couple households, 21.5% were households with a male householder and no spouse or partner present, and 33.2% were households with a female householder and no spouse or partner present. About 32.5% of all households were made up of individuals and 10.9% had someone living alone who was 65 years of age or older.
There were 2,264,966 housing units, of which 7.9% were vacant. Among occupied housing units, 54.3% were owner-occupied and 45.7% were renter-occupied. The homeowner vacancy rate was 1.7% and the rental vacancy rate was 7.5%.
Racial and ethnic composition +Cook County, Illinois – Racial and ethnic compositionRace / Ethnicity (NH = Non-Hispanic)Pop 1980Pop 1990Pop 2000Pop 2010 Pop 2020% 1980% 1990% 2000% 2010% 2020White alone (NH)3,271,4792,915,6342,558,7092,278,3582,135,24362.27%57.11%47.59%43.86%40.47%Black or African American alone (NH)1,336,0701,301,1961,390,4481,265,7781,185,60125.43%25.49%25.86%24.37%22.47%Native American or Alaska Native alone (NH)8,2147,7436,7546,6825,6550.16%0.15%0.13%0.13%0.11%Asian alone (NH)111,602181,285257,843318,869408,6912.12%3.55%4.80%6.14%7.75%Native Hawaiian or Pacific Islander alone (NH)x included in the Asian category in the 1980 Censusx included in the Asian category in the 1990 Census1,5431,043961xx0.03%0.02%0.02%Other race alone (NH)26,9685,0157,2917,75120,5380.51%0.10%0.14%0.15%0.39%Mixed race or Multiracial (NH)x not an option in the 1980 Censusx not an option in the 1990 Census82,41371,432136,074xx1.53%1.38%2.58%Hispanic or Latino (any race)499,322694,1941,071,7401,244,7621,382,7789.50%13.60%19.93%23.96%26.21%Total5,253,6555,105,0675,376,7415,194,6755,275,541 100.00%100.00%100.00%100.00%100.00%
Racial / Ethnic Profile of places in Cook County, Illinois (2020 Census)Following is a table of towns and census designated places in Cook County, Illinois. Data for the United States (with and without Puerto Rico), the state of Illinois, and Cook County itself have been included for comparison purposes. The majority racial/ethnic group is coded per the key below. Communities that extend into and adjacent county or counties are delineated with a followed by an accompanying explanatory note. The full population of each community has been tabulated including the population in adjacent counties. Majority minority with no dominant groupMajority WhiteMajority BlackMajority HispanicMajority Asian