A view of urban Catholicism, The Immigrant Church focuses on the people in the pews and furnishes a comparison of Irish and German Catholic life in mid-nineteenth-century New York City. Nearly one-half of the city's population in 1865 consisted of Irish and German Catholics. Singling out three parishes (one Irish, one German, and one a mixed group of Germans and Irish), Dolan examines the role of religion in strengthening group life in these ethnic communities, traces the development of the Catholic Church in the city, and reveals the relationship between urban and church growth.