Yellowstone County leans Republican by roughly 26 points: about 37% of voters vote Democratic and 63% Republican.
About 77% of adults in Yellowstone County typically vote, above the U.S. average of about 62%. Among adults in Yellowstone County, ~29% vote Democratic, ~48% Republican, and ~23% don't vote. The map below shows estimated turnout by block group.
How Yellowstone County compares
Among counties within 50 miles, Yellowstone County is the least Republican-leaning.
Yellowstone County runs about 5 points more Republican than Montana as a whole.
Politics vary noticeably by city within Yellowstone County. The northwest side is the most Republican-leaning (R+45) and the south side is the least Republican-leaning (R+23), a spread of about 22 points.
Why Yellowstone 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 Yellowstone County, not a ranked or complete list of what matters most.
Yellowstone County votes Republican even though it is densely developed (about 72%, far above the Montana average of 13%). State and regional patterns outweigh the Democratic lean that density usually predicts here.
Preventive-care access and voter turnout
Places with strong routine preventive-care access tend to turn out at a higher rate; Yellowstone County, MT sits above the national average 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 Yellowstone County looks the way it does
Areas with high high-school completion turn out at higher rates. About 96% of adults in Yellowstone County have completed high school, about 6 points above the U.S. average of 90%. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Stillwater County, MT R+57
- Carbon County, MT R+38
- Musselshell County, MT R+64
- Golden Valley County, MT R+69
- Big Horn County, MT Even
- Sweet Grass County, MT R+54
- Treasure County, MT R+66
- Wheatland County, MT R+66
- Big Horn County, WY R+73
- Park County, WY R+51
Counties with Similar Populations
- Maui County, HI D+19
- Ector County, TX R+42
- Rock County, WI Even
- Houston County, GA R+4
- Olmsted County, MN D+12
- Charles County, MD D+38
- Hampshire County, MA D+45
- Portage County, OH R+12
- Johnson County, IN R+35
- Dorchester County, SC R+12
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Sources and methodology
Precinct-level voting records used to fit the model come from Montana Secretary of State, 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.