With a revolution behind them, a continent before them, and the First Amendment protecting them, religio-sexual pioneers in antebellum America were free to strike out on their own, breaking with the orthodoxies of the past. Shakers followed the ascetic path; Oneida Perfectionists accepted sex as a gift from God; and Mormons redefined marriage in light of new religious revelations that also redefined God, humankind, spirit, and matter. Sex became a powerful way for each group to reinforce their sectarian identity as strangers in a strange land. Sex and Sects tells the story of these three religiously inspired sexual innovations in America: the celibate lifestyle of the Shakers, the Oneida Community’s system of controlled polyamory, and plural marriage as practiced by the Mormons. Stewart Davenport analyzes why these bold experiments rose and largely fell over the course of the nineteenth century within the confines of the new American republic. Moving beyond a social-scientific lens, Davenport traces for the first time their fascinating shared trajectory as they emerged, struggled, institutionalized, and declined in tandem—and sheds historical light on the way in which Americans have discussed, contested, and redefined the institutions of marriage and family both in our private lives and in the public realm.