This dissertation explores the place of black Catholicism in urban culture by tracing the history and legacy of St. Elizabeth's parish (1873-1949), St. Louis' most prominent black parish and one of the most influential black parishes nationally. I argue that to understand black Catholicism historians must examine how black Catholics imagined themselves as part of three overlapping social worlds: the black diaspora, the Catholic church, and the local parish. Rather than viewing urban life as a patchwork of discrete communities, this borderland approach to the city views individuals as existing in multiple, shifting, and often conflicting social worlds. I suggest that Catholicism provided a framework of rights and responsibilities and an ecclesiastical structure for blacks to push for representation within the Church, and that black Catholics helped make St. Elizabeth's a borderland for interracial interaction and a base for social action for the larger black community. A focus on how clack Catholics created hybrid identities as blacks, Catholics, and members of local parishes shows how black history and Catholic history are intertwined and provides important lessons in this age of fragmented identity politics about how to balance multiple commitments and identities.