This dissertation explains why Sylvester Graham, a popularizer of physiology in the antebellum United States, believed that he announced a new gospel of health, and why many hundreds of his contemporaries came to see vegetarianism, teetotalism, and all-around hygiene as the necessary foundation of their faith. These explanations require a broader inquiry into the ways early nineteenth-century Americans understood their bodies, their souls, and connections between the two in a world upturned by new sciences, changing theologies, and expanding markets. Combining the moral agency of Arminian theology with the rising confidence of physiological science, health reformers offered Americans an optimistic program for self-improvement through self-discipline. Bodily and spiritual reinvigoration achieved through proper regimen, reformers promised, would empower people to enjoy the promise of the antebellum marketplace revolution while avoiding its perils. Although the promise often went unrealized, this heady concoction of commitments nevertheless helped forge the individualist ideology that defines American healthcare to this day. Thus, while this dissertation charts the convergence of religion and health in a movement that never captured all Americans' attention, it simultaneously traces an origin story of a far more powerful and ubiquitous ideology: the belief that, in health and in economic affairs, just as in religion, individuals are responsible for their own fate.