Illinois Counties
Illinois County map
Click Image to Enlarge

Illinois Counties

There are one hundred and two counties in Illinois. St. Clair County was the first county established in what is today Illinois. Most counties in Illinois were named after early American leaders, especially of the American Revolutionary War, as well as soldiers from the Battle of Tippecanoe and the War of 1812.

Cook County, Illinois

Cook County Education, Geography, and HistoryCook County, Illinois Courthouse

Cook County is a county in the United States state of Illinois. Based on the 2010 census, the population was 5,194,675. Cook County was created on January 15, 1831. The county seat is Chicago, the third-most populous city in the United States. This county is named for Daniel Pope Cook (1794-1827), politician and first Attorney General of Illinois.

Cook County is included in the Chicago-Naperville-Elgin, IL-IN-WI Metropolitan Statistical Area. It is surrounded by the five collar counties.

Etymology - Origin of Cook County Name

The county is named for Daniel P. Cook, pioneer lawyer, first Attorney General of Illinois and member of Congress (1819-1827).


County QuickFacts: CensusBureau Quick Facts

Cook County History

Cook County was created on January 15, 1831 (Laws, 1831, p. 54) and was formed from Putnam County. Present area, or parts of it, formerly included in: Putnam County (1825-1831), Fulton County (1823-1825), Pike County (1821-1823), Clark County (1819-1821), Crawford County (1816-1819), Edwards County (1815-1816), Madison County (1812-1815), St. Clair County (1801-1812) and Knox, Northwest Territory (1795-1801).

The County was named for Daniel Pope Cook. In 1819, Cook was elected to Congress as the sole representative from Illinois. In Congress, Cook served on the committee on Public Lands and later on the Ways and Means Committee. He secured a grant of government lands to aid in the construction of the Illinois-Michigan Canal. In 1824, he had as sole congressman from Illinois cast the vote of the state for Adams, thus practically deciding the decision. Daniel Cook always suffered from poor health and died October 16, 1827, at the age of 33. Four years after his death, a county in Illinois was named in his honor. He probably never visited the area we call Cook County. The County Seat is Chicago (1831-Present).

 With more than 40 percent of all Illinois residents, it is the most populous county in Illinois and the second-most populous county in the United States after Los Angeles County, California. Cook County's population is larger than that of 29 individual US states and the combined populations of the seven smallest states. There are 135 incorporated municipalities partially or wholly within Cook County, the largest of which is Chicago, which makes up approximately 54% of the population of the county. That part of the county which lies outside of the Chicago city limits is divided into 30 townships. Geographically the county is the fifth largest in Illinois by land area and shares the state's Lake Michigan shoreline with Lake County. Including its lake area, the 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. Cook County's land is mainly urban and very densely populated.

Cook County is an urban county in the upper northeastern section of the State of Illinois that contains more than 800 local governmental units within its boundaries. With a population of approximately 5.3 million people, it is the second most populous county in the nation and the 19th largest government in the United States (2005 census statistics).

It is a home rule county pursuant to Article VII, Section 6 of the Illinois State Constitution and is governed by a 17-member Board of Commissioners who are elected from single-member districts. The Commissioners and a County Board President are elected to four-year terms by the citizens of the County.

Cook County contains 128 municipalities in its region, the most well known being the City of Chicago - which is the County seat where the central offices of Cook County are located. The City of Chicago and the suburban municipalities account for approximately 85% of the County's 946 square miles, while unincorporated areas make up the remaining 15%. The unincorporated areas of the County are under the jurisdiction of the Cook County Board of Commissioners.

Geography: Land and Water

As reported by the Census Bureau, the county has a total area of 1,635 square miles (4,235 km2), of which 946 square miles (2,449 km2) is land and 689 square miles (1,785 km2) (42.16%) is water, most of it in Lake Michigan.

Cook county is located in northeast Illinois. Chicago Portage National Historic Site and Pullman National Monument are located in this county.

Neighboring Counties

Bordering counties are as follows:

  • North: Lake County
  • East: Lake Michigan
  • Southeast: Lake County, Ind.
  • Southwest: Will County
  • West: DuPage County; Kane County
  • Northwest: McHenry County


Compare More Colleges and Universities
Find the Right School

Find more schools to match to your needs.

County Resources
US Counties
Click Image to Enlarge