Illinois Voter Check

Cook County, Illinois

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Cook County, Illinois
Daley Plaza 060716 — CC BY-SA 2.5, User:JeremyA · source

About Cook County

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.

Description adapted from Wikipedia, CC BY-SA 4.0.

Cook County at a glance

County seat
Chicago
Population
5,194,625 (2025)
Land area
1,635 sq mi
Founded
1831

Largest communities in Cook County

  1. Chicago County seat2,746,388
  2. Thornton Township157,865
  3. Wheeling Township157,487
  4. Worth Township152,934
  5. Proviso Township151,209

History of Cook County

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.

Adapted from Wikipedia, CC BY-SA 4.0.

Start here

Confirm you're ready to vote in Cook County

  1. 01

    Run a guided check

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  2. 02

    Ask Cook County directly

    Your county election office handles registration, mail ballots, and polling places.

    Cook County election office →

Official channels

Cook County election resources

Statewide tools and every Illinois resource in one place: the Illinois page at Scan Check Protect →

Neighboring counties

Part of Illinois Voter Check

This is the Cook County page of Illinois Voter Check, a project of True the Vote, pointing Illinois voters at the official tools that already exist — and at Scan Check Protect to verify your registration.

Where anything here differs from what Cook County or the Illinois State Board of Elections publishes, they are right and this page is not.