57631 is a Republican stronghold. About 12% of voters here vote Democratic and 88% Republican.
About 50% of adults in 57631 typically vote, below the U.S. average of about 62%. Among adults in 57631, ~6% vote Democratic, ~44% Republican, and ~50% don't vote. The map below shows estimated turnout by block group.
How 57631 compares
Among zip codes within 15 miles, 57631 is the most Republican-leaning.
57631 runs about 47 points more Republican than South Dakota as a whole.
Politics vary noticeably by block within 57631. The west side is the most Republican-leaning (R+79) and the northeast side is the least Republican-leaning (R+65), a spread of about 14 points.
Why 57631 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 57631, not a ranked or complete list of what matters most.
Rural areas vote Republican. About 3% of residents in 57631 live in densely developed areas, about 6 points below the South Dakota average of 9%.
Developed land and Republican lean
Places with a rural land-use pattern tend to lean Republican; 57631, SD sits in the bottom tenth nationally on this measure. Developed land does not change how people vote; it mostly reflects how urban a place is.
Why turnout in 57631 looks the way it does
Turnout in 57631 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 Zip Codes
Zip Codes with Similar Populations
Sources and methodology
Precinct-level voting records used to fit the model come from South Dakota 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.