Illinois is on track to lose one of its 18 congressional seats following the 2020 census, marking a significant shift in representation for the state. With a population that has steadily declined over the past six years, Illinois joins Vermont, Connecticut, and West Virginia as one of the few states experiencing negative growth, according to a Brookings Institution study.
Population Decline: A Six-Year Trend
Illinois last saw population growth in 2013, when it reached nearly 12.9 million residents. Since then, the state has experienced a steady decline, with the population falling to approximately 12.65 million—a net loss of nearly 250,000 people.
The reasons for this decline are widely debated, ranging from high taxes and political corruption to economic challenges and climate. Regardless of the cause, the consequences are clear: Illinois will lose representation in Congress, with other Midwestern states such as Michigan, Minnesota, and Ohio also likely to see minimal growth. Meanwhile, states like Texas and Florida, which have experienced over 15% growth in the past decade, are poised to gain seats.
Congressional Representation and Census Impact
The U.S. Constitution requires a decennial census to determine representation in the House of Representatives and allocate federal funding. Currently, Illinois’ 18 congressional districts each represent about 745,000 people.
With a population loss of nearly 200,000 since the last census, Illinois is guaranteed to lose at least one seat. A more severe undercount—like the 19.3% nonresponse rate seen in 2010—could push that loss to two seats. Illinois has invested $29 million to improve census participation and avoid such an outcome.
Political Implications: Who Will Lose the Seat?
The loss of a congressional seat will inevitably affect either Republicans or Democrats, depending on which district is eliminated.
Downstate Districts in the Crosshairs
Political experts predict the seat most likely to disappear is in downstate Illinois. Congressional Districts 15 (R), 12 (R), and 13 (R) are among those with the greatest population losses. With Republicans representing these areas and the Democratic-controlled state legislature leading redistricting efforts, it’s expected that Republicans will bear the brunt of the reduction.
John Jackson of Southern Illinois University notes, “The 15th District, currently held by Republican John Shimkus, who is not seeking re-election, is the most likely candidate for elimination.” Democrats, who control the statehouse, are unlikely to cut their own representation.
Challenges for Democrats Downstate
Christopher Mooney, a political science professor at the University of Illinois Chicago, highlights the challenge Democrats face in downstate districts. “With further population losses, Democrats might struggle to create a viable district in downstate Illinois,” he says. Attempts to consolidate Democratic voters could result in oddly shaped districts that stretch to find supportive constituencies.
The Unlikely Loss of a Second Seat
If Illinois loses a second seat, the impact could shift to the Cook and Collar County areas. Democrats have gained ground in traditionally Republican strongholds like DuPage, Lake, and McHenry counties, but if these districts flip back to the GOP, the loss could harm Democrats instead.
A Broader National Shift
While Illinois grapples with its losses, Republican-leaning states such as Texas, which is expected to gain three seats, will benefit from population growth. The potential shift could offset GOP losses in Illinois and other Midwestern states.
What’s Next?
The 2020 census results will shape Illinois’ political landscape for the next decade. Redistricting battles will intensify as lawmakers and party leaders negotiate which districts to eliminate. With the potential for contentious debates and court challenges, the loss of congressional seats reflects a broader trend of demographic and political shifts across the country.