Documents engineering activities, land acquisition, and property management through both internal correspondence between Commission members and external correspondence with the public and other entities. Includes general correspondence organized by decade, correspondence related to specific park sections (East Fairmount Park, West Fairmount Park, Wissahickon Valley Park, Cobbs Creek, Tacony Creek, Pennypack Creek), art and sculpture matters, land acquisitions, design and construction projects, and engineering notes. The correspondence illuminates Commission operations and demonstrates the evolving public perception of the park system.