More than seventy pediatric seashore hospitals lined the coasts of the northeastern United States and western Europe in the late 19th and early 20th centuries. Founded as responses to urban industrial life, physicians, reformers, and families sent poor children from their city homes to seaside hospitals with the belief that the marine environment would rebuild children's health and bodies. This dissertation examines American seashore hospitals, focusing on the Children's Seashore House (CSH) in Atlantic City, NJ. I argue that these institutions created a "healthscape," a therapeutic vision of the seashore that inextricably bound health to leisure, and children to their environments. This healthscape could only exist in contrast to urban centers, and the dissertation begins with an examination of the ways in which working-class families and social workers shared a view of the city - including the homes it harbored - as inimical to children's health. Medical knowledge substantiated these views, and helped construct the seashore's salubrity. Chapter two explores the ideology of marine medication. I argue that physicians rationalized natural therapeutics, dosing and distilling the environment into its therapeutic elements, which placed marine medication within mainstream medical practices. Bringing working-class children and their mothers to seashore hospitals was meant to both restore their health and instill middle-class value structures. Chapter three examines how the CSH's built environments reflected those objectives. Then shifting from practitioners to patients, chapter four illuminates that by maintaining their urban caregiving networks and performing marine medication for middle-class tourists, working-class families were critical contributors to defining the seashore as a space where health and leisure were inextricably bound. Despite their popularity, seashore hospitals began to decline by the 1930s. Chapter five uses UV lamps to explore how "technologies of nature" reproduced nature's beneficial effects and rendered the seashore unnecessary to children's health. I conclude with a discussion of the vestiges of marine medication today, including the recent rediscovery that the seashore can improve pediatric patients' health.