University of Illinois Urbana‑Champaign

Geographic Region: Congressional Districts

Illinois is divided into 17 congressional districts, with each district representing roughly 750,000 people in the U.S. House of Representatives.

Illinois flag on pole waving in breeze

All site-based data (e.g., child care) and almost all demographic data (e.g., population) are available by congressional district on the IECAM database. Non-site-based data (e.g., early intervention, home visiting) are not presented by congressional district.

After each decennial census conducted by the U.S. Census Bureau, the congressional districts for each state are redrawn. The new districts are the basis for the next general election, and they take effect in the Congress after that election. (For example, the latest decennial census was conducted in 2020. The new districts were redrawn in 2021, and they were used as the basis for the general election in November 2022. They took effect with the beginning of the next Congress in January 2023.)

After the 2020 Census, Illinois lost one district..

Source of definition: U.S. Census Bureau

Comparing congressional districts across decennial censuses

In IECAM’s online database and multiyear search feature, the congressional districts drawn after the 2010 census will be considered one region type and the districts based on the 2020 census will be considered yet another region. Data available for the 18 districts based on the 2010 census include demographic data for years 2011 through 2021 and service data for years 2011 through 2022. Data available for the 17 districts based on the 2020 census begins with 2022 demographic data and 2021 site-based service data.

Because these region types have different numbers of districts (18 for the post-2010 census, 17 for the post-2020 census) and because the districts cover different geographic areas, it is not possible to compare data for post-2010 and post-2020 census districts.

However, you are able to compare data for different years that apply to the post-2010 and post-2020 census districts. For example, you can compare data on PFA capacity or population of children for Congressional District 15 in 2012 and in 2013, and you can compare the same data for Congressional District 15 in 2022 and in 2023 when those data become available.

Below find the two most recent congressional district maps for Illinois. The districts change boundaries only after each decennial Census (every 10 years).

Post-2020 Census districts

Post-2010 Census districts