The college years represent a prime opportunity for students to develop prosocial skills through friendships that cross social boundaries (i.e., in which the two friends differ on at least one aspect of sociocultural identity such as race, political affiliation, or religion). By cultivating empathy and reducing social stratification, these friendships may serve as a needed remedy for the ongoing and deepening tribalism dominating the current U.S. political climate, ultimately advancing a more justice-oriented society. We utilized data from 55 focus groups with 268 participants at 18 U.S. institutions of various sizes, locations, and affiliations to explore how campus environments and experiences influence college students' boundary-crossing friendships. Participants highlighted how aspects of their campus climates (size, structural diversity, norms, and identity support) encouraged as well as discouraged crossing social boundaries. They discussed how programs (curricular and co-curricular), spaces (residence and dining halls, prayer spaces), and informal social opportunities (such as studying, dining, socializing, or having meaningful conversations) helped them develop and deepen friendships across the social boundaries of religious, secular, and spiritual (RSS) identity; political beliefs; race/ethnicity; and other identities. They also described the power of early campus experiences in setting the stage for crossing social boundaries. Our findings add texture to prior quantitative research documenting the power of campus conditions and environments for fostering friendship across social boundaries, and they illuminate effective ways for colleges and universities to create environments and experiences that provide students with opportunities and reasons to connect and build friendships that bridge social divisions.