This dissertation examines opposition to nuns and convent life in America as it was expressed through vigilante violence, propaganda literature, and party politics. While nuns may seem like an unlikely target of hostility, a vast cohort of Americans singled them out as a serious threat to the republic. Between 1830 and 1860 anti-convent propaganda, including Awful Disclosures of the Hotel Dieu by “escaped nun†Maria Monk, flooded the literary market. Monk’s work warned of a Catholic conspiracy in the United States through the cloister, depicted alleged horrors of convent life, and cast nuns variously as masculine tyrants, foolish slaves, and whores. Investigators quickly unveiled Maria Monk as an impostor, but her book became the second best-seller after Uncle Tom’s Cabin before the Civil War, and it has never gone out of print. In order to “protect†American women from the nun’s life, mobs stormed convents from Massachusetts to Maryland. By the 1850s, suspicion of nuns became formally politicized by Know-Nothing legislators who established “Nunnery Committees†for convent investigations. Although the Civil War quieted the outcry against nuns for a time, the campaign against convents had far-reaching implications. Members of the second Ku Klux Klan relied on anti-convent propaganda to buttress their positions, and common stereotypes of nunsâ€"first evident in nineteenth-century convent narrativesâ€"have also persisted in popular culture. This dissertation argues that the campaign against nuns and convent life was a much greater part of nineteenth-century American popular culture and politics than previous historians have recognized.