Williamson County leans heavily Republican by roughly 36 points: about 32% of voters vote Democratic and 68% Republican.
About 75% of adults in Williamson County typically vote, above the U.S. average of about 62%. Among adults in Williamson County, ~24% vote Democratic, ~51% Republican, and ~25% don't vote. The map below shows estimated turnout by block group.
How Williamson County compares
Among counties within 50 miles, Williamson County leans more Republican than 4 of 19 neighbors.
Williamson County runs about 47 points more Republican than Illinois as a whole. Illinois leans Democratic overall, while Williamson County is one of the few Republican-leaning pockets.
Politics vary noticeably by city within Williamson County. The northeast side is the most Republican-leaning (R+52) and the west side is the least Republican-leaning (R+26), a spread of about 26 points.
Why Williamson County leans the way it does
This analysis examined 14,881 data points per county to find what predicts political lean and turnout. The items below are a few correlations that stood out for Williamson County, not a ranked or complete list of what matters most.
Williamson County votes against the grain of Illinois. Illinois leans Democratic overall, while Williamson County runs about 47 points more Republican. Car-dependent areas vote Republican, and about 83% of residents in Williamson County drive to work alone, above 86% of counties.
Housing overcrowding and voter turnout
Places with low overcrowding tend to turn out at a higher rate; Williamson County, IL sits in the bottom tenth nationally on this measure.
Why turnout in Williamson County looks the way it does
Turnout in Williamson County sits close to the national pattern. Routine healthcare access, homeownership, education, and food security all land near their national averages here. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Franklin County, IL R+52
- Jackson County, IL D+7
- Johnson County, IL R+41
- Saline County, IL R+50
- Union County, IL R+48
- Perry County, IL R+49
- Hamilton County, IL R+62
- Pope County, IL R+60
- Jefferson County, IL R+44
- Pulaski County, IL R+26
Counties with Similar Populations
- Aroostook County, ME R+30
- Rice County, MN Even
- Jones County, MS R+32
- Jefferson County, AR D+22
- Spalding County, GA R+8
- Butler County, KS R+41
- St. Francois County, MO R+48
- Ionia County, MI R+30
- Laurens County, SC R+35
- Oldham County, KY R+23
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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.