Within the Roman Catholic Church, the pope serves a dual role as both the Bishop of Rome and the spiritual and symbolic leader of the Church as a whole. According to Catholic doctrine, the pope is the ultimate arbiter of Church tradition and, in specific cases, his teachings are recognized as infallible in matters of faith and morals. As the global personification of Catholicism, the institution of the papacy has exerted a strong influence on American religion, culture, and politics, shaping not only how Catholics expressed their religious beliefs, but how they were viewed by their Protestant neighbors. Throughout American history, Catholicism in general and the papacy in particular has sparked periodic attacks by "nativist" Protestants who saw newly arriving Catholic immigrants as detrimental or dangerous to American society. In the nineteenth century, this resulted in several riots in northern cities and the burning of Catholic...