Breed History research and clippings files contain both originals and photocopies of Mastiff articles, pamphlets, illustrations, research notes, kennel ads, show reports/results, pedigrees, registrations, ephemera and further published information dating back to 1890 1970s and 1980s candid photographs and win shots originally present in the files, have been removed and stored separately. Some items are relate to organizations such as the American Mastiff Club and Old English Mastiff Club (including a catalog from its first ever show in 1890). Canadian pedigrees, champion and breeder lists, and a collection of photographs and plates of late-19th century Mastiff champions are also present. A small personal collection of the Chapman family, prominent early 20th-century British breeders, contains images of their two major imports, Mattesdon Tondelayo and Bernardo of Pinetrees, and correspondence regarding the donation of the latter to the Yale University Peabody Museum of Natural History for study supporting their breed preservation program.
The Club Administration files hold records of the club's functions and operations dating back to 1938: constitution and by-laws revisions, news bulletins and memos, meeting minutes, officer correspondence, memebership lists, financial documents and receipts, officer nominations and ballots, committee reports, questionnaires, documentation of the organizations the Canadian Mastiff Club and North & East Mastiff Fanciers, and more. The files appear to have been assembled by the club's historian-archivist Patricia Hoffman, whose personal letters and judges ribbon from the first MCOA independent specialty in 1983 are present in addition to correspondence establishing the mission of the club archives. The late 1980s, a tumultuous period suggesting a need for rehaul of club administration, are chronicled. Documents retained by Marissa Clements between 1985 and 2008, including meeting minutes and Judges Education Commitee materials, have been maintained separately.
Dog Shows materials include marked catalogs, premium lists, various handouts, and photographs dating back to the first independent independent MCOA Specialty in 1983. Some MCOA show committee, related correspondence, and other materials are present but researchers are also advised to consult the Club Administration files. Also present is audovisual footage of the 2007 Specialty and a small selection of ribbons, medals, and other souvenirs from MCOA and other events.
Publications and Printed Matter features the parent club’s newsletters as well as many regional and select international newsletters. The MCOA’s first newsletter was published in 1965, with the name "The Journal" added in the fall of 1974. The earliest newsletters, and issues of the later "MCOA Bulletin," are in the collection, complimenting the runs held by the AKC Library. Newsletters for organizations the Midwest Mastiff Fanciers, Old English Mastiff Club Nederland, Canadian Mastiff Club, and more are present in addition to a substantive run of the Old English Mastiff Club newsletter (as well as a handbook and annual report for the EDMC). MCOA breed columns for the AKC Gazette and further Mastiff articles, pamphlets, books, and ephemera round out this group.
The Canine Health and Genetic Data contains a Dysplasia Control Registry (1974-2001) and a variety of further health registries, reports, and related correspondence dating between 1992 and 2000, including collaboration and communications with the Canine Eye Registration Foundation and Institute for Genetic Disease Control in Animals.
The bulk of the Mastiff Club of America (MCOA) collection documents the period beginning in the 1970s when the Mastiff breed signficicantly raised in popularity, which also required dedicated work to combat puppy mills and overbreeding.