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 difference-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 effect heterogeneity for attitudes towards Black individuals and policies promoting racial equity, but (positive) impacts and geographic variation are smaller in magnitude relative to those observed for conservatism. Investigations into mechanisms suggest that this heterogeneity may depend on the effectiveness of integration policies. In the south, White-Black exposure was greater following desegregation, and White disenrollment was lower. Finally, I demonstrate that results are robust to concerns of bias resulting from potential non-random in- and out-mobility of individuals into integrating contexts. My study provides the first causal evidence on how theories concerning intergroup contact and racial attitudes (i.e., the contact hypothesis) may have applied to school contexts following historic court mandates to desegregate. [The paper will be published in "Education Finance and Policy."]