Today we might take them for granted, but at the turn of the twentieth century planned public play spaces were uncommon. In the nation’s booming cities, children played in streets, alleys, and vacant lots, largely unsupervised. Reformers were concerned that the lack of open space, play equipment, and adult supervision led to decreased physical activity, increased risk of traffic accidents, and exposure to unhealthy habits and criminal behavior. Due in large part to the advocacy of groups such as the Outdoor Recreation League and the Playground Association of America, thousands of municipal playgrounds, many of which are still open today, were built in towns and cities across the nation, making playgrounds a widely accepted feature of the public landscape.
https://blogs.loc.gov/teachers/2018/05/how-the-playground-movement-made-a-case-for-play/?loclr=eatlcb
