The PlayGround gets scholarly today, with a look at this post from the 2013 Carnegie International blog on the history of playgrounds (with cool old pictures of Pittsburgh playgrounds):
"At the turn of the last century, it wasn’t the aim of playgrounds to provide fun for children. Back then, playgrounds were part of a clear social and educational agenda. The Playground Movement and the American Settlement Movement (an important progressive reform initiative at the end of the 19th century) fought both for the improvement of the mental and physical health in lower-income classes and immigrants."
Read more from Gabriela Burkhalter, who just moved from Switzerland to Pittsburgh, but still runs Architektur für Kinder (Architecture for Children), a homepage dedicated to the history of playgrounds.
(photo above is from Duncan Park in Lawrenceville, from the PG archives)