The fonds represents forty years of the photographic work of Mary Cairns and consists of slides, copy prints, contact prints, and negatives as well as a scrapbook of ribbons and prizes and notes concerning her life and photographic technique. Images are primarily of Prince Edward Island although there are some from trips to Europe, Nova Scotia, New Brunswick and Alberta. The two major series of images document the flora and fauna of Prince Edward Island and Island churches. The fonds has been divided into the following series:

Series 1: Nature
Series 2: Farm life
Series 3: P.E.I. Scenes
Series 4: Travel
Series 5: People & events
Series 6: P.E.I. Churches
Series 7: Competition prints
Series 8: Background material

There may be some overlap in the contents of the series.