Does living near members of another social group breed tolerance or hostility? This is a long-standing question in political science, with evidence pointing in multiple directions. While experiments confirm that intergroup contact can promote positive attitudes, observational studies show that real-world conditions often fail to produce positive outcomes.In this dissertation, I examine factors that determine how outgroup context shapes group attitudes. I analyze survey responses describing individuals’ interactions with and opinions about various social groups. By combining these responses with census data about the demographic contexts in which respondents live, I can determine how contextual factors shape different components of outgroup attitudes. Through this analysis, I find that living near members of an outgroup is associated both with an increased probability of interacting with outgroup members, and with an increased perception of group threat. These in turn shapes outgroup stereotypes: contact challenges negative stereotypes, while threat reinforces them. Finally, these stereotypes inform an overall positive or negative outgroup attitude. This leaves the question of whether the positive effects of contact or the negative effects of threat will dominate. I find that engaging in frequent contact with outgroup members can overcome the negative effects of threat. Contextual factors determine when contact will be common and promote tolerance, and when it will be uncommon and allow threat to produce hostility. Previous studies have highlighted the role of segregation in reducing opportunities for contact, but I introduce another factor: language. Living near English-speaking outgroup members provides English monolinguals with more opportunities for contact, leading to more positive attitudes, while living near non-English-speaking outgroup populations reinforces negative stereotypes, leading to more negative attitudes. These contextual effects of language are not limited to outgroup attitudes. I find that English-monolingual ingroup members similarly exhibit less ingroup identification and more negative ingroup attitudes when living in contexts where many ingroup members do not speak English.