In 2004, controversy erupted in Hamtramck, Michigan, when a mosque began to broadcast the azan (Islamic call to prayer) in this historically Polish-Catholic enclave. While several Christian leaders rushed to support the mosque in the name of religious freedom and toleration, many of their congregants, who were anxious about their community’s changing demographics, asserted a legal right not to hear these religious “others.” Through an analysis of this public dispute, this dissertation examines how religious communities respond to diversity and how American law shapes inter-religious contact in pluralistic urban environments. It argues that how American Christians respond to religious “others” reveals assumptions both about what it means to be Christian and what it means to be American. This case study has at least three implications for the study of contemporary American Christianity. First, while focusing on relations between Christian and Muslim communities, it calls attention to the alliances and divisions which cut within and across religious boundaries. Second, this dissertation studies how religious congregations act publicly in ways that both respect and push against the limits set by American law. Finally, it considers how religious leaders deal with differences between clergy and laity about how to respond to diversity.