When the French Revolution degenerated into violent factionalism and civil war during the early 1790s, American conservative northeasterners reacted in profound terror. Alarmed by the possibility that the United States would follow her “sister republic” into chaos and civic bloodshed, northern Federalists and their Congregationalist allies reacted by aggressively attacking the violence of the French Revolution and its supposed American votaries. The Reign of Terror in America argues that American fears of the violence of the French Revolution led to antislavery, antiwar, and public education movements in the nineteenth-century United States. It is the first history of how Americans perceived the Reign of Terror, and reveals how significantly fears of French Violence changed the United States. Ultimately, these fears inspired a stark opposition to the violence of slaveholding, provided material for dramatic attacks on southern slavery, and helped to spark the Civil War.