Castle Shannon leans slightly Democratic by roughly 10 points: about 55% of voters vote Democratic and 45% Republican.
About 77% of adults in Castle Shannon typically vote, above the U.S. average of about 62%. Among adults in Castle Shannon, ~42% vote Democratic, ~35% Republican, and ~23% don't vote. The map below shows estimated turnout by block group.
How Castle Shannon compares
Among cities within 25 miles, Castle Shannon leans more Democratic than 201 of 250 neighbors.
Castle Shannon runs about 12 points more Democratic than Pennsylvania as a whole.
Politics vary noticeably by neighborhood within Castle Shannon. The west side is the most Democratic-leaning (D+22) and the east side is the least Democratic-leaning (D+3), a spread of about 19 points.
Why Castle Shannon 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 Castle Shannon, not a ranked or complete list of what matters most.
Dense areas vote Democratic. More than 99% of residents in Castle Shannon live in densely developed areas, about 63 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and Castle Shannon sits in the top quarter (about 37%, above 84% of cities). A high never-married share predicts Democratic voting, and about 42% of adults in Castle Shannon have never been married, above 95% of cities.
Population density and Democratic lean
Places with high population density tend to lean Democratic; Castle Shannon, PA sits in the top tenth nationally on this measure.
Why turnout in Castle Shannon looks the way it does
Areas with high high-school completion turn out at higher rates. About 97% of adults in Castle Shannon have completed high school, about 5 points above the Pennsylvania average of 91%. Learn more about the findings and methodology on the political spectrum map.
Nearby Cities
- Dormont, PA D+39
- Brentwood, PA D+14
- Baldwin, PA D+3
- Bethel Park, PA D+5
- Mount Oliver, PA D+41
- Green Tree, PA D+10
- Upper St. Clair, PA D+12
- Pleasant Hills, PA D+6
- Heidelberg, PA D+10
- Carnegie, PA D+7
Cities with Similar Populations
- Orlovista, FL D+34
- Millstadt, IL R+37
- Friday Harbor, WA D+42
- Dormont, PA D+39
- Wadesboro, NC D+22
- Monticello, FL R+17
- Baldwin Harbor, NY D+39
- Mountainside, NJ Even
- Castroville, TX R+33
- Trinity, TX R+53
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Sources and methodology
Precinct-level voting records used to fit the model come from Pennsylvania Department of State, Bureau of 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.