63109 leans heavily Democratic by roughly 44 points: about 72% of voters vote Democratic and 28% Republican.
About 75% of adults in 63109 typically vote, above the U.S. average of about 62%. Among adults in 63109, ~54% vote Democratic, ~21% Republican, and ~25% don't vote. The map below shows estimated turnout by block group.
How 63109 compares
Among zip codes within 15 miles, 63109 leans more Democratic than 31 of 71 neighbors.
63109 runs about 63 points more Democratic than Missouri as a whole. Missouri leans Republican overall, while 63109 is one of the few Democratic-leaning pockets.
Politics vary noticeably by block within 63109. The northeast side is the most Democratic-leaning (D+63) and the southwest side is the least Democratic-leaning (D+30), a spread of about 33 points.
Why 63109 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 63109, not a ranked or complete list of what matters most.
Dense areas vote Democratic. More than 99% of residents in 63109 live in densely developed areas, about 64 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and 63109 sits in the top quarter (about 53%, above 91% of zip codes). 63109 runs against the grain of Missouri, a Democratic-leaning pocket in a Republican-leaning state.
Population density and Democratic lean
Places with high population density tend to lean Democratic; 63109, MO sits in the top tenth nationally on this measure.
Why turnout in 63109 looks the way it does
Areas with high high-school completion turn out at higher rates. About 96% of adults in 63109 have completed high school, about 7 points above the Missouri average of 89%. 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.