The Mary Sheldon Barnes Papers consist of eight linear feet of correspondence, creative and professional writings, artwork, juvenilia, line-a-day diaries, notes, teaching materials, memorabilia, scrapbooks, and photographs. The material dates from 1857 to 1948 (bulk dates 1880 to 1898). Although Barnes did not work directly with women's history, her papers provide a particularly interesting insight into the personal and professional life of an academic woman historian of the late 19th century and the relationship between two academic scholars. They also are a valuable source of information on historiography.

There are additional Mary Sheldon Barnes papers housed at Penfield Library, Special Collections, State University of New York at Oswego. Earl Barnes' papers, the Sheldon Family Papers, and faculty papers of Mary's four siblings are also in the Penfield Library.

This collection is organized into four series:

• I. Biographical Material
• II. Correspondence
• III. Writings
• IV. Photographs and Memorabilia