Sioux County is a Republican stronghold. About 22% of voters here vote Democratic and 78% Republican.
About 91% of adults in Sioux County typically vote, above the U.S. average of about 62%. Among adults in Sioux County, ~20% vote Democratic, ~71% Republican, and ~9% don't vote. The map below shows estimated turnout by block group.
How Sioux County compares
Among counties within 50 miles, Sioux County leans more Republican than 11 of 13 neighbors.
Sioux County runs about 42 points more Republican than Iowa as a whole.
Politics vary noticeably by city within Sioux County. The northeast side is the most Republican-leaning (R+72) and the southeast side is the least Republican-leaning (R+41), a spread of about 31 points.
Why Sioux 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 Sioux County, not a ranked or complete list of what matters most.
Areas with many family households vote Republican. About 74% of households in Sioux County are family households, about 7 points above the U.S. average of 67%.
Preventive-care access and voter turnout
Places with strong routine preventive-care access tend to turn out at a higher rate; Sioux County, IA sits in the top 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 Sioux County looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Sioux 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 70%, about 10 points above the U.S. average of 60%. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Lyon County, IA R+65
- Plymouth County, IA R+49
- O'Brien County, IA R+54
- Osceola County, IA R+57
- Union County, SD R+43
- Cherokee County, IA R+42
- Lincoln County, SD R+29
- Rock County, MN R+45
- Woodbury County, IA R+9
- Clay County, SD D+2
Counties with Similar Populations
- Hill County, TX R+58
- Livingston County, IL R+38
- Adams County, IN R+60
- Washington County, TX R+37
- Floyd County, KY R+61
- Greene County, PA R+43
- Miami County, IN R+45
- Greenup County, KY R+52
- Cocke County, TN R+65
- Laclede County, MO R+61
Sources and methodology
Precinct-level voting records used to fit the model come from Iowa 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.