Brigham Young and Thomas L. Kane first met on the plains of western Iowa in 1846 The Mormon prophet and the Philadelphia reformer would go on to exchange more than one hundred letters over the next three decades. This annotated collection of their correspondence reveals a great deal about these two remarkable men, while also providing crucial insight into nineteenth-century Mormonism and the historical moment in which the movement developed. Until his death in 1877, Young guided the religious, economic, and political life of the Mormon community, whose settlements spread throughout the West and provoked a profound political, legal, and even military confrontation with the American nation. Young relied on Kane, 21 years his junior, as his most trusted outside adviser, making Kane the most important non-Mormon in the history of the Church. In return, no one influenced the direction of Kane's life more than Young. The surviving letters offer crucial insights into Young's personal life and views as well as his actions as a political and religious leader. The correspondence reveals the strategies of the Latter-day Saints in relating to American culture and government during these crucial years when the "Mormon Question" was a major political, cultural, and legal issue. The letters also shed important light on the largely forgotten "Utah War" of 1857-58, triggered when President James Buchanan dispatched a military expedition to ensure federal supremacy in Utah and replace Young with a non-Mormon governor. The Prophet and the Reformer offers a complete reproduction of the exchange between Young and Kane, and provides an introduction to each letter that contextualizes and analyzes it.