McHenry County leans slightly Republican by roughly 6 points: about 47% of voters vote Democratic and 53% Republican.
About 83% of adults in McHenry County typically vote, above the U.S. average of about 62%. Among adults in McHenry County, ~39% vote Democratic, ~44% Republican, and ~17% don't vote. The map below shows estimated turnout by block group.
How McHenry County compares
Among counties within 50 miles, McHenry County leans more Republican than 10 of 13 neighbors.
McHenry County runs about 16 points more Republican than Illinois as a whole. Illinois leans Democratic overall, while McHenry County is one of the few Republican-leaning pockets.
Politics vary noticeably by city within McHenry County. The southeast side runs the most Democratic (Even) and the northeast side runs the most Republican (R+16), a spread of about 18 points.
Why McHenry 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 McHenry County, not a ranked or complete list of what matters most.
McHenry County votes Republican even though it is densely developed (about 64%, far above the Illinois average of 33%). State and regional patterns outweigh the Democratic lean that density usually predicts here. A high family-household share predicts Republican voting, and about 74% of households in McHenry County are family households, above 92% of counties. McHenry County runs against the grain of Illinois, a Republican-leaning pocket in a Democratic-leaning state.
Renting and voter turnout
Places with homeowner-heavy households tend to turn out at a higher rate; McHenry County, IL sits in the bottom tenth nationally on this measure.
Why turnout in McHenry County looks the way it does
Areas with strong routine healthcare access turn out at higher rates. McHenry County is in the top quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. The dental-visit rate here is about 67%, about 7 points above the U.S. average of 60%. Homeowners vote more often than renters, and about 84% of households in McHenry County own their home, above 94% of counties. High high-school completion lines up with higher turnout, and about 94% of adults in McHenry County have completed high school, above 81% of counties. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Lake County, IL D+22
- Kane County, IL D+13
- Boone County, IL R+15
- Walworth County, WI R+17
- Kenosha County, WI Even
- DeKalb County, IL D+3
- DuPage County, IL D+14
- Winnebago County, IL D+7
- Racine County, WI D+7
- Cook County, IL D+42
Counties with Similar Populations
- Lubbock County, TX R+23
- Northampton County, PA Even
- Lorain County, OH R+5
- Rockingham County, NH D+6
- Albany County, NY D+30
- Cumberland County, ME D+29
- Gloucester County, NJ R+2
- St. Louis City, MO D+65
- Greene County, MO R+18
- Escambia County, FL R+13
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.