This book reveals the origins of the American religious marketplace by examining the life and work of reformer and journalist Orestes Brownson (1803-1876). Grounded in a wide variety of sources, including personal correspondence, journalistic essays, book reviews, and speeches, this work argues that religious sectarianism profoundly shaped participants in the religious marketplace. Brownson is emblematic of this dynamic because he changed his religious identity seven times over a quarter of a century. Throughout, Brownson waged a war of words opposing religious sectarianism. By the 1840s, however, a corrosive intellectual environment transformed Brownson into an arch religious sectarian. The book ends with a consideration of several explanations for Brownson religious mobility, emphasizing the goad of sectarianism as the most salient catalyst for change.