The Modern Period examines how and why Americans adopted radically new methods of managing and thinking about menstruation during the twentieth century. In the early twentieth century women typically used homemade cloth "diapers" to absorb menstrual blood, avoided chills during their periods to protect their health, and counted themselves lucky if they knew something about menstruation before menarche. New expectations at school, at play, and in the workplace, however, made these menstrual traditions problematic, and middle-class women quickly sought new information and products that would make their monthly periods less disruptive to everyday life. Lara Freidenfelds traces this cultural shift, showing how Americans reframed their thinking about menstruation. She explains how women and men collaborated with sex educators, menstrual product manufacturers, advertisers, physical education teachers, and doctors to create a modern understanding of menstruation. Excerpts from seventy-five interviews-accounts by turns funny and moving-help readers to identify with the experiences of the ordinary people who engineered these changes. The Modern Period ties historical changes in menstrual practices to a much broader argument about American popular modernity in the twentieth century. Freidenfelds explores what it meant to be modern and middle class and how those ideals were reflected in the menstrual practices and beliefs of the time. This accessible study sheds new light on the history of popular modernity, the rise of the middle class, and the relationship of these phenomena to how Americans have cared for and managed their bodies.