63121 is a Democratic stronghold. About 89% of voters here vote Democratic and 11% Republican.
About 55% of adults in 63121 typically vote, below the U.S. average of about 62%. Among adults in 63121, ~49% vote Democratic, ~6% Republican, and ~45% don't vote. The map below shows estimated turnout by block group.
How 63121 compares
Among zip codes within 15 miles, 63121 leans more Democratic than 55 of 69 neighbors.
63121 runs about 97 points more Democratic than Missouri as a whole. Missouri leans Republican overall, while 63121 is one of the few Democratic-leaning pockets.
Politics vary noticeably by block within 63121. The east side is the most Democratic-leaning (D+86) and the west side is the least Democratic-leaning (D+69), a spread of about 17 points.
Why 63121 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 63121, not a ranked or complete list of what matters most.
Dense areas vote Democratic. More than 99% of residents in 63121 live in densely developed areas, about 63 points above the U.S. average of 36%. A high never-married share predicts Democratic voting, and about 53% of adults in 63121 have never been married, above 96% of zip codes. 63121 runs against the grain of Missouri, a Democratic-leaning pocket in a Republican-leaning state.
Preventive-care access and voter turnout
Places with limited routine preventive-care access tend to turn out at a lower rate; 63121, MO sits in the bottom quarter 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 63121 looks the way it does
Renters vote less often than owners. About 46% of households in 63121 rent, about 21 points above the U.S. average of 25%. Limited routine healthcare access lines up with lower turnout, and 63121 sits in the bottom quarter on routine-care measures. High food insecurity lines up with lower turnout, and about 32% of adults in 63121 report food insecurity, above 95% of zip codes. 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 Missouri 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.