This dissertation argues that the Old School Presbyterian Church was a significant 'bond of union' to the American nation during the antebellum era. How did a phrase from the Presbyterian constitution, describing the relationship of the Presbyterian General Assembly to its congregations come to play such a central role in how Old School Presbyterians thought of their role in the civil Union? There are several interwoven questions that this dissertation will seek to answer. One set of questions involves the problem of disestablishment: given that the United States rejected the concept of an established church, what would church/state relations look like? The transformation in identity from 'church' to 'denomination' took time. The older understanding of the unity–or catholicity–of the visible church could not help but be eroded as 'liberty of conscience' began to trump catholicity. A second constellation of questions revolves around ethnicity and culture. An overwhelming proportion of Old School Presbyterians were of Scottish and Ulster descent. Virtually every debate spawned numerous appeals to Scottish Presbyterian beliefs and practices. Even non-Scottish Presbyterians seem to have adopted the Scottish heritage of their co-religionists. While considered theologically antiquated by many for their confessional Calvinism, Old School Presbyterians also lived in the mainstream of social, economic, and political power. A third array of issues probes the intellectual milieu. The constitutional issues underlying the ecclesiological disputes of the Old School are central for understanding why they took the positions that they did with respect to slavery, education and other social issues. Commonsense moral reasoning, with its emphasis on universally accessible moral intuitions, produced an emphasis on persuasion, both in written and oral debate. This dissertation relies upon records of oral debates more than many previous works. With Methodists and Baptists divided north and south, and the less numerous Episcopalians largely residing in urban areas, Old School Presbyterians were the only Protestant denomination with significant representation in every region of the nation. This dissertation explains how the imagined self-concept of 'the bond of union' influenced the Old School's decision-making process in debates over education, slavery, temperance, marriage, and church order.