In this paper I study how school desegregation by race following "Brown v. Board of Education" affected White individuals' racial attitudes and politics in adulthood. I use geocoded nationwide data from the General Social Survey and differences-in-differences to identify causal impacts. Integration significantly reduced White individuals' political conservatism as adults in the U.S. South but not elsewhere. I observe similar geographic impact heterogeneity for individuals' attitudes towards Blacks and policies promoting racial equity, but positive effects emerge less consistently across specifications. Results suggest that this heterogeneity may depend on the effectiveness of integration policies. In the south, Black-White exposure was greater following desegregation, and White disenrollment was lower. My study provides the first causal evidence on how different theories concerning intergroup contact and racial attitudes (i.e., the contact and racial threat hypotheses) may have applied to school contexts following historic court mandates to desegregate.