61603 leans heavily Democratic by roughly 46 points: about 73% of voters vote Democratic and 27% Republican.
About 50% of adults in 61603 typically vote, below the U.S. average of about 62%. Among adults in 61603, ~37% vote Democratic, ~14% Republican, and ~49% don't vote. The map below shows estimated turnout by block group.
How 61603 compares
Among zip codes within 15 miles, 61603 leans more Democratic than 23 of 27 neighbors.
61603 runs about 36 points more Democratic than Illinois as a whole.
Politics vary noticeably by block within 61603. The west side is the most Democratic-leaning (D+59) and the northeast side is the least Democratic-leaning (D+30), a spread of about 29 points.
Why 61603 leans the way it does
This analysis examined 14,881 data points per zip code to find what predicts political lean and turnout. The items below are a few correlations that stood out for 61603, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 93% of residents in 61603 live in densely developed areas, about 56 points above the U.S. average of 36%. A high never-married share predicts Democratic voting, and about 49% of adults in 61603 have never been married, above 94% of zip codes.
Preventive-care access and voter turnout
Places with limited routine preventive-care access tend to turn out at a lower rate; 61603, IL sits in the bottom tenth nationally on this measure. Dental visits do not drive turnout; the rate reflects income, insurance, and healthcare access, which line up with who votes.
Why turnout in 61603 looks the way it does
Areas with limited routine healthcare access turn out at lower rates. 61603 is in the bottom quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. The dental-visit rate here is about 48%, about 15 points below the Illinois average of 63%. Renters vote less often than owners, and about 47% of households in 61603 rent, about 22 points above the U.S. average of 25%. High food insecurity lines up with lower turnout, and about 34% of adults in 61603 report food insecurity, above 96% of zip codes. Learn more about the findings and methodology on the political spectrum map.
Nearby Zip Codes
Zip Codes with Similar Populations
Sources and methodology
Precinct-level voting records used to fit the model come from Illinois State Board of Elections, distributed by the Voting and Election Science Team. Demographic inputs come from the U.S. Census Bureau (ACS 5-year estimates and the 2020 Decennial Census). Health and environmental inputs come from the CDC (PLACES and the Environmental Justice Index). Land cover comes from the USGS and EPA. Election-day and lead-up weather come from PRISM 4km daily grids and the NOAA Global Historical Climatology Network. Mail-voting and election-administration patterns come from the MIT Election Lab's Survey of the Performance of American Elections. Block-group crime detail comes from CrimeGrade. Internet data and modeling support provided by ISPreports.org.
Modeling and analysis by the BestNeighborhood data science team. Full methodology and findings: political spectrum map.
Methodology reviewed by the BestNeighborhood data team. Last updated May 2026.