This article explores the history of breastfeeding in postwar America and places it within a larger framework of the intersections of science, culture, and gender. Through an exploration of the history of breastfeeding at its nadir, it argues that the movement back to the breast that became visible in the 1970s was rooted in the emergence of the ideology of natural motherhood in the decades surrounding World War II. Natural motherhood relied upon a scientific understanding of nature and motherhood in which interconnected physiological and emotional processes unfolded instinctually in the bodies of mothers and infants along a largely predetermined pattern. Through an analysis of scientific and prescriptive literature on family, child rearing, and sexuality, and the letters of women themselves, this article seeks to understand the persistent choices of mothers to breastfeed in this period and asks what meaning the practice held.