Illinois district maps divide the state into 17 congressional districts, 59 state Senate districts, and 118 state House districts, all redrawn after the 2020 Census. Every address in the state falls inside one of each. You can look up which districts cover your home, and who represents you in them, through the Illinois State Board of Elections.
Look Up Your Districts by Address
The Illinois State Board of Elections runs a “Find My Elected Officials” tool that takes your home address and returns your congressional district, state Senate district, and state House district along with the officials serving each seat.1Illinois State Board of Elections. Find My Elected Officials The Illinois General Assembly’s website also publishes boundary descriptions and maps for the current state legislative districts.2Illinois General Assembly. Illinois Constitution – Article IV
These tools match your address against the census block data used when the lines were drawn. If you recently moved, or your home sits close to a district boundary, the final call on which district you belong to comes from your county clerk or Board of Election Commissioners. It’s worth checking before any election, especially after a redistricting year when familiar lines may have shifted.
What the Three Maps Cover
Congressional Districts
Illinois sends 17 members to the U.S. House of Representatives, one from each congressional district. The state had 18 seats before the 2020 Census and lost one because population growth trailed states in the South and West.3United States Census Bureau. Congressional Apportionment 2020 Census Brief The federal census, conducted every ten years, is what determines how many seats each state gets.4U.S. Census Bureau. About Congressional Apportionment With the drop to 17, every district now contains roughly 754,000 residents.
The shape of these districts varies with population density. In the Chicago metropolitan area, a congressional district can be compact enough to cover only a handful of neighborhoods. Downstate, a single district can stretch across dozens of counties and hundreds of miles of farmland and small towns to hit the same population target.
State Senate and House Districts
The Illinois Constitution nests the two chambers together. The state is divided into 59 Senate districts, and each Senate district is split into exactly two House districts, giving 118 House seats.2Illinois General Assembly. Illinois Constitution – Article IV You have one state senator and one state representative, and their territories overlap so that your House district is always inside your Senate district.
The same constitutional article requires all these districts to be compact, contiguous, and substantially equal in population.2Illinois General Assembly. Illinois Constitution – Article IV Federal courts have generally treated a total population deviation greater than 10 percent between the largest and smallest state legislative districts as presumptively unconstitutional, though states can justify larger deviations for compelling reasons.
How the Maps Get Drawn
The Illinois General Assembly holds primary authority to draw new district maps in the year after each federal census.2Illinois General Assembly. Illinois Constitution – Article IV Lawmakers use census data to write a redistricting plan, and the plan moves through the normal legislative process: both chambers pass it, and the governor signs or vetoes it. Congressional maps are drawn as ordinary legislation. State legislative maps follow the same first path but have a constitutional backup if it stalls.
State law also requires a minimum of four public hearings for the House and four for the Senate before new legislative lines are finalized. Legislators have sometimes scheduled more. These hearings give residents a chance to testify about community boundaries, shared interests, and how proposed lines would affect their areas.
The Backup Commission
If no state legislative redistricting plan takes effect by June 30, the Illinois Constitution triggers a backup process. A Legislative Redistricting Commission of eight members must be formed by July 10, split so that no more than four members belong to the same political party.2Illinois General Assembly. Illinois Constitution – Article IV The House Speaker, House Minority Leader, Senate President, and Senate Minority Leader each appoint one legislator and one non-legislator to the commission.
The commission must file an approved plan with the Secretary of State by August 10, with at least five of the eight members voting in favor. If the commission deadlocks, the Illinois Supreme Court submits the names of two people from different political parties to the Secretary of State by September 1. The Secretary of State then publicly draws one name at random by September 5, and that person becomes the tie-breaking ninth member. The expanded commission has until October 5 to file a final plan approved by at least five members.2Illinois General Assembly. Illinois Constitution – Article IV
Because the ninth member effectively gives one party control of the final map, the random draw carries substantial political stakes. The mechanism has been criticized as reducing redistricting to a coin flip when the parties can’t agree, but it remains what the constitution provides.
Legal Limits on Where the Lines Can Go
Two federal doctrines shape every Illinois map. First, both chambers of a state legislature must be apportioned based on population, under the Supreme Court’s 1964 decision in Reynolds v. Sims.5Justia. Reynolds v Sims, 377 US 533 (1964) That is why Illinois has to redraw its legislative maps after every census to account for population shifts within the state.
Second, Section 2 of the Voting Rights Act prohibits any voting standard or practice that denies the right to vote on account of race, color, or membership in a language minority group.6Office of the Law Revision Counsel. 52 USC 10301 – Denial or Abridgement of Right to Vote on Account of Race or Color A violation is established when, under the totality of circumstances, the political process is not equally open to a protected class, giving them less opportunity to elect representatives of their choice. In practice, this often leads to majority-minority districts in areas like Chicago where minority communities are large and concentrated enough to form one. The Supreme Court in Thornburg v. Gingles set the threshold conditions for such a claim: the minority group must be large enough and compact enough to form a majority in a single district, it must be politically cohesive, and the white majority must vote as a bloc that usually defeats the minority group’s preferred candidates.7Justia. Thornburg v Gingles, 478 US 30 (1986)
Partisan Versus Racial Gerrymandering
Illinois maps have drawn repeated accusations of partisan gerrymandering, and the courts have drawn a firm line on what they will hear. In 2019, the U.S. Supreme Court ruled in Rucho v. Common Cause that partisan gerrymandering claims are political questions federal courts have no authority to resolve.8Legal Information Institute. Rucho v Common Cause Complaints about partisan advantage must be directed at Springfield or pursued through the state courts.
Racial gerrymandering is different. Federal courts will intervene when race is the predominant factor in drawing district lines, overriding traditional criteria like compactness and respect for political boundaries. If a challenger proves race dominated the process, the court applies strict scrutiny, meaning the state must show a compelling interest and that the district was narrowly tailored to serve that interest.9Congress.gov. Racial Vote Dilution and Racial Gerrymandering Courts evaluate this district by district, not by looking at the state map as a whole.
Two Census Data Quirks That Affect the Maps
The population figures behind these maps come from the decennial census, but they are not raw headcounts. Starting with the 2020 Census, the Bureau adopted a disclosure avoidance method called differential privacy, which introduces small statistical variations into the data to prevent reverse-engineering of individual responses.10United States Census Bureau. Understanding Differential Privacy The noise is small enough at the district level that it doesn’t meaningfully distort counts for congressional or legislative districts. At the level of individual census blocks, the variations can be more noticeable and occasionally complicate the fine-grained line-drawing that redistricting requires.
The federal Census Bureau also counts incarcerated people at their prison location rather than their home address. Because Illinois has several large correctional facilities in rural areas, this can inflate rural district counts while undercounting the urban communities where most incarcerated people lived before imprisonment. Illinois has enacted legislation to adjust for this in future redistricting cycles by counting prisoners at their home addresses.