Castlewood is a Republican stronghold. About 22% of voters here vote Democratic and 78% Republican.
About 77% of adults in Castlewood typically vote, above the U.S. average of about 62%. Among adults in Castlewood, ~17% vote Democratic, ~60% Republican, and ~23% don't vote. The map below shows estimated turnout by block group.
How Castlewood compares
Among cities within 25 miles, Castlewood leans more Republican than 19 of 30 neighbors.
Castlewood runs about 27 points more Republican than South Dakota as a whole.
Why Castlewood leans the way it does
This analysis examined 14,881 data points per city to find what predicts political lean and turnout. The items below are a few correlations that stood out for Castlewood, not a ranked or complete list of what matters most.
Areas with many family households vote Republican. About 79% of households in Castlewood are family households, about 12 points above the U.S. average of 67%.
Park access and Republican lean
Places with low park coverage tend to lean Republican; Castlewood, SD sits in the bottom tenth nationally on this measure. Park access does not change how people vote; it tends to track denser, higher-income areas.
Why turnout in Castlewood looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Castlewood 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 71%, about 11 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 96% of adults in Castlewood have completed high school, above 80% of cities. Learn more about the findings and methodology on the political spectrum map.
Nearby Cities
- Kones Corner, SD R+65
- Stone Bridge, SD R+50
- Estelline, SD R+52
- Thomas, SD R+78
- Goodwin, SD R+56
- Hayti, SD R+73
- Lake Poinsett, SD R+55
- Foley, SD R+54
- Kranzburg, SD R+56
- Watertown, SD R+40
Cities with Similar Populations
- St. Helena, NC R+18
- Medford, OK R+68
- Osceola, NE R+60
- DeBord, KY R+64
- Elwood, KS R+46
- Hamler, OH R+60
- Bristol, ME D+16
- Antwerp, NY R+45
- Woodlawn, KY R+50
- Fairfield Center, ME R+27
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.