Defined here as the introduction or conservation of outdoor vegetation in cities, urban greening has bloomed during periods of intensive urbanization. This was true in the nineteenth century and it seems to be the case again today, as a range of greening practices is co-arising during a third, and perhaps final, period of global urbanization. Human health has been a recurring theme underlying the enduring aspiration to integrate nature with city. Using change over time as a conceptual frame, this paper offers a comparative assessment of municipal greening in the nineteenth and early twenty-first centuries, focusing on the potential implications upon, and the relationship between, such activity, urban design, and public health. In so doing, the narrative bridges theory, science, and practice, and dovetails with discourse on urban ecosystem services. Part one assesses prominent drivers and types of greening in nineteenth-century industrial cities, a pioneering period in this evolving narrative. Part two reviews contemporary literature on the human health benefits of urban green spaces, and draws comparisons to the Industrial Era. Part three explores potential links between contemporary greening practice and scholarship on related health benefits, wherein proximal greening emerges as a distinct form, and possible norm, for twenty-first-century urban design.