Floods of immigration and rapid industrialization and urbanization in America at the turn of the century set in motion the transformation of many long-established institutions. This book examines specific ways in which cultural changes affected the structure of the religious establishment. Statistical models are applied to United States Census data from 1890 and 1906 on city and church populations, revealing connections between the growth of cities, the increase in literacy, and the formation of ethnic subcommunities that led to a new level of religious diversity. The author analyses evidence of growing competition among churches and of a level of individual commitment to congregations, demonstrating that the patterns of religious community established at the turn of the century provided the basis for the current denominational system. The author further analyses the relationship of religious diversity to urban secularization, as well as its role as a catalyst to sectarian conflict. In offering a quantitative assessment of issues central to the history of American religion, this book is a significant contribution to the study of religion in America.