Many have argued that American Unitarianism originated solely from within Congregationalism and developed independent of outside influences. William Ellery Channing's "Unitarian Christianity" sermon in 1819 was a key moment in the history of the denomination, as Channing consciously sought to define the parameters of the faith and eliminate all vestiges of competing influences. Yet the American Unitarian tradition was far more complex than its nineteenth-century adherents were willing to admit. In Joseph Priestley and English Unitarianism in America, J. D. Bowers reexamines its origins, course, and development and subsequently reveals the extent to which Joseph Priestley's ideas concerning Congregational polity were recognized and established within the United States. In contrast to studies that simply trace the history of the denomination as it flows out of New England and is controlled by Bostonians, Bowers shows that Priestley's legacy grew in importance throughout the nineteenth century and held sway throughout many of the frontier regions of the nation. By discussing the complexity of interdenominational rivalry, lack of central control, and a continuous transatlantic exchange among religious liberals, he shows that English Unitarianism continued to serve as an essential and noteworthy foundation for subsequent developments within the American denomination as it endured the challenges of Protestant orthodoxy, unregulated liberalism, Transcendentalism, and the never-ending quest to define liberal religion in America. This is an insightful account of an often neglected set of tenets and developments in the denomination's history. It uniquely traces the course of continued English influence as it established a new point of reference for understanding the dynamic origins of denominational development, Unitarian thought, and liberal religion.