This article explores the genesis of small parks in Tokyo following the 1923 Great Kantō Earthquake. It sheds new light on an example of innovative urban design and post-disaster reconstruction, and highlights the growing place that children occupied in the minds of bureaucrats and urban planners. The small parks were designed for children first and foremost. Originally conceived as a means to increase space for school children to play and exercise, all 52 parks were strategically located beside primary schools. As the state's goals of social management expanded, however, officials increasingly recognized the potential to use small parks as sites of rest and guided recreation, as well as emergency refuge. A history of Tokyo's small parks thus offers a window in to the growing understanding about the relationship between the built environment, health and society in inter-war Japan.