Voting in the United States has long been known to divide sharply along racial lines, and the degree of racially polarized voting evidently varies across regions, and even within a state. Researchers have further studied variation in racially polarized voting using aggregate data techniques, but these methods assume that variation in individual preferences is not related to geography. This paper presents estimates based on individual level data of the extent and variation in racially polarized voting across US Congressional Districts. Leveraging large, geocoded sample surveys, we develop an improved method for measuring racial voting patterns at the Congressional District-level. The method overcomes challenges in previous attempts of survey modeling by allowing survey data to inform the synthetic population model. This method has sufficient power to provide precise estimates of racial polarization even when survey data are sparse. We find that variation across districts but within states explains roughly 20 percent of the total variation; states explain a further 20 percent of the total variation, and 55 percent of the variation is simply national differences between races. The Deep South still has the highest racial polarization between White and Black voters, but some Midwestern congressional districts exhibit comparably high polarization. The polarization between White and Hispanic voters is far more variable than between Black and White voters.