57639 is a Democratic stronghold. About 79% of voters here vote Democratic and 21% Republican.
About 47% of adults in 57639 typically vote, below the U.S. average of about 62%. Among adults in 57639, ~37% vote Democratic, ~10% Republican, and ~53% don't vote. The map below shows estimated turnout by block group.
How 57639 compares
Among zip codes within 15 miles, 57639 leans more Democratic than 2 of 4 neighbors.
57639 runs about 87 points more Democratic than South Dakota as a whole. South Dakota leans Republican overall, while 57639 is one of the few Democratic-leaning pockets.
Why 57639 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 57639, not a ranked or complete list of what matters most.
57639 votes against the grain of South Dakota. South Dakota leans Republican overall, while 57639 runs about 87 points more Democratic. A high never-married share predicts Democratic voting, and about 47% of adults in 57639 have never been married, above 93% of zip codes.
Walkability and Republican lean
Places with a low walkability score tend to lean Republican; 57639, SD sits in the bottom tenth nationally on this measure. A walkable street grid does not change how people vote; it mostly reflects how urban a place is.
Why turnout in 57639 looks the way it does
Areas with limited routine healthcare access turn out at lower rates. 57639 is in the bottom quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. Renters vote less often than owners, and about 44% of households in 57639 rent, about 19 points above the U.S. average of 25%. High-crime urban areas turn out at lower rates, and 57639 sits in the top 15% on a violent-crime measure. 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.