Abstract: Through an analysis of the published discourse of nine prominent social reformers of the Progressive era (1880-1914) and an examination of their life circumstances, this dissertation explores the themes of religious idealism and nationalism which figured prominently in the early formulation of modern liberal reform ideology in the United States. During this period of unprecedented immigration and rapid urbanization, this closely knit group of liberal Protestant clergyman, academic social scientists and settlement house leaders were consumed with the task of reconciling the changed social conditions with their often vague and ethnocentric notions of American civilization. While the sense of common cause and cooperation which existed among the individuals in this study may be surprising to the contemporary observer, their alliances came about naturally in a time when both the modern university and the social sciences were in their first stages of development. The clergy associated with the social gospel movement were not at all reluctant to opine on social and economic issues in public forums and academic journals; neither was it uncommon for leaders of the settlement movement and activist professors to invoke religious rhetoric in their calls for reform. This study illuminates how a variety factors were responsible for the secular trend in the rhetoric of progressive social reform at the end of this period and which continued during the New Deal and War on Poverty. A specific focus will be placed on tracing themes of the America's millennial destiny and how they gradually evolved into prophesies of social transformation through the applied use of social expertise. While these religious roots have been largely overlooked by more recent generations of social progressives, the enduring consequences of how this first generation of reformers thought, spoke and wrote provides a unique perspective from which to survey American social welfare history. Through understanding this distant era when social progressivism was closely associated with liberal Protestant religiosity and nationalism, it will be possible to more fully comprehend the present conservative era in which the rhetoric of individualism and personal piety are being invoked to change the shape of social policy.