An interactive web-based visualization mapping municipal and private gymnasiums across Boston’s wards between 1909 and 1922, with time-series attendance data across nearly fifteen years. The map reveals how public gymnasiums were strategically placed in immigrant-heavy neighborhoods as part of a broader moral reform agenda, while private gymnasiums clustered in middle-class districts. The visualization reveals a sharp decline in attendance in 1918, when most of the city’s gymnasiums, particularly those near the harbor, were repurposed as overflow hospitals during the influenza pandemic.