The Mary M. Marks photograph collection consists of approximately 301 glass plate negatives (with modern paper prints) and 24 prints without negatives. The images are from the Oro Grande Placer Mine and the Gold Pan Mining Company and include mining pits, dredges, flumes, and various other mining operations. Other images are of railroad depots and homes in Summit County Colorado (Breckenridge and Dillon), as well as the Snake River. Also included are photographs of Mary Marks's friends especially Allice Miller, Kate Schwalbach, and Mary's husband John H Marks. Also part of the ecollection are two oversize boxes with maps and engineering plans for different mines and portions of Colorado. Some of her photographs were used in mining prospectus publications. She documented the mining, prospecting, and machinery, but also focused on artistic and aesthetic elements of the photography and included men and women in her photographs of the Colorado mining. In her photography, Mary Marks climbed to the top of observation platforms, and down into the mining pits. Some photographs were taken with a 4x5 view camera while others were taken with a larger frame. From what is known, Marks did not label the negatives themselves, but would label their envelopes and coverings.