This critical narrative history examines the development of sociology in the United States during what has come to be labeled as the Progressive Era, roughly the years from the 1890s to World War I. Despite the label, this era was defined as much by social problems associated with industrialization, urbanization, and immigration as by the growth of its cities and the wealth of its capitalists. We explore the roots of American sociology in the transition of protestant theology from Calvinism to its reformation in the social gospel, the simultaneous development of settlement houses, and the “creation” of sociology as the science of reform.