Extensive research on racial contexts suggests that white Americans living near black Americans adopt more negative racial attitudes. Theoretically, local intergroup exposure has been conceptualized as acting contemporaneously through various mechanisms. However, a separate body of research on political socialization indicates that adolescent experiences are often especially influential. We hypothesize that whites’ racial contexts during adolescence produce prejudiced responses. We then test this hypothesis using two complementary data sets, a population-based panel conducted 2007–13 and the Youth-Parent Socialization Panel Survey (1965–97). Our analyses demonstrate the enduring influence of adolescent contexts at larger levels of aggregation: while the racial composition of whites’ current counties is not a consistent predictor of racial prejudice, the racial composition of their county during high school is. Proximity during one’s formative years increases racial prejudice years later, providing new insights about local contextual effects and the roots of racial prejudice.