Founded in 1936, the Tredyffrin Easttown Historical Society is the oldest community organization on the Upper Main Line in suburban Philadelphia conducting local historical research and collecting local historical resources pertaining to the townships of Tredyffrin and Easttown in eastern Chester County, Pennsylvania. Continuously since 1937 the Society has published Tredyffrin Easttown History Quarterly, a periodical focused on Upper Main Line history. The Society holds over 35 linear feet of archival materials dating from 1732 to the present, such as photographs, glass plate negatives, genealogy and local history research materials, school records, correspondence, minute books, financial records, and other family papers and organizational records.