This dissertation explores social reform in antebellum and Civil War America through a biography of Thomas L. Kane (1822-1883). A member of a prominent Philadelphia family, Kane crusaded most prominently against slavery and in defense of the Mormons' religious liberty. He represents a crucial community of reformers who challenge the traditional narrative of nineteenth-century reform, which presents antebellum reform as springing from the convergence of Whig politics and evangelical religion. By contrast, the roots of Kane and similar reformers came from the Democratic Party, anti-evangelicalism, and romanticism. The antebellum Democratic Party had a significant reform wing, driven by the party's egalitarianism and more inclusive vision of religious and ethnic pluralism. These reformers declared war on human suffering and sought to defend the downtrodden. While many remained traditionally religious, others, like Kane, reacted against evangelical reform because of their own antipathy to evangelicalism (though he converted in mid-life to Christianity). Most eventually became Republicans (often with a stop in Free Soil). Antislavery and other nineteenth-century reforms owe as much, if not more, to these reformers as to their evangelical counterparts. In the 1840s, Kane found the ideal object of his sympathies in the reviled Mormons. For the next four decades, he was the Mormons' most trusted outside supporter and adviser. To counter the popular perception of Mormons as dangerous fanatics, Kane cast them as a sincere religious minority searching for liberty. His dramatic mediation between Mormons and government officials in 1858 brought a peaceful end to the Utah War and earned him national fame. Kane's life also illuminates the influences of the 'culture of honor' (typically associated only with the South) and romanticism on nineteenth-century culture and reform. Kane's ethic of honor particularly shaped his Civil War career, in which he led the famous Pennsylvania Bucktails and became a Brigadier General. In addition, Kane emulated the cultural type of the romantic hero. As such, he preferred decisive action over contemplation; iconoclasm over conformity; individual judgment over social norms; and personal courage over upper-class comforts. Kane's life thus illuminates a world of mid-nineteenth-century reform shaped by Democratic ideology, anti-evangelicalism, and romanticism.