Civil War soldiers enjoyed unprecedented access to obscene materials of all sorts, including mass-produced erotic fiction, carte de visite, playing cards, and stereographs. With a series of antebellum legal, technological, and commercial developments as a foundation, the concentration of men into armies ushered in a wartime triumph of pornography. Illicit materials entered camps in haversacks, through the mail, or sold by sutlers; soldiers found it discarded on the ground and civilians discovered it in abandoned camps. Little of it survived the war, though, as soldiers did not keep it and archives did not collect it. Even so, porn raised concerns among reformers and lawmakers who launched a postwar campaign to combat it. At the war’s end, a victorious, resurgent nation-state sought to assert its moral authority by redefining human relations of the most intimate sort, including the regulation of sex and reproduction, most evident in the Comstock Laws, a federal law and a series of state measures outlawing pornography, contraception, and abortion. Sex and the Civil War is the first book to take the erotica and pornography that men read and shared seriously and to link the postwar reaction to porn to debates about the future of sex and marriage.