The Mabelle Campbell photograph collection includes six photo albums, thirty-nine loose photos, two Philadelphia Rapid Transit Company Hiking Club Lists, and nine pamphlets from the Leidy Microscopical Club. The albums, photos, and papers document excursions of the Delaware Valley Naturalists Union from 1894-1939. According to a conversation with Mrs. Campbell in 1980, most of the photographs were taken by Harold Palmer

This collection is arranged chronologically.