For over 125 years, Philadelphians and visitors from around the world have delighted in discovering Smith Memorial Playground and Playhouse, a hidden gem within the city's sprawling Fairmount Park. Since opening in 1899, at the bequest of Richard and Sarah Smith, this unique play space, complete with a mansion purpose-built to support young children's play, has provided a respite from city heat, connection to nature, and myriad opportunities for child-directed play and family recreation. The playground's beloved Ida Newman wooden slide, originally built in 1905, has delighted generations of children. The evolution of Smith's Playground and Playhouse and the numerous other programs and facilities it ran across the city over its first 125 years follows the development and theories of the playground movement and other child-saving campaigns of the 19th and 20th centuries. Using the rich visual material in the Smith Memorial Playground and Playhouse Archives, housed at the Special Collections Research Center at Temple University's Charles Library, as well as holdings at other regional archives, former Smith board member, landscape architect, and play advocate Anna Forrester and play movement scholar Dr. Deborah Shine Valentine provide a nuanced, well-researched tribute to one of Philadelphia's unique historic spaces.