We propose that individuals are more politically active in more like-minded social environments. To test this hypothesis, we combine administrative data from the Federal Election Commission and the U.S. Postal Service. We identify 45,000 individuals who contributed to Barack Obama’s 2008 presidential campaign and changed residences either before or after the 2012 election cycle.We examine whether living in an area with a higher share of Democrats causes higher contributions to Obama. We find that conformity effects are economically significant. Additionally, we conduct counterfactual analysis that shows that these effects are important for understanding geographic polarization.