This fonds represents the records of a family long-established in Ontario, as collected and preserved by the genealogist Marshall Macdougall Dean.

As a genealogist, Marshall Macdougall Dean collected and wrote about the Dean family and others in his lineage, and was a founding member of the Canadian Society of Mayflower Descendants. He was born in Fort William, lost his siblings, father, and mother at a fairly young age, and spent much of his later life in and near Toronto.

His father, Marshall Blanchard Dean, trained as a physician at the University of Toronto before moving to Fort William. In addition to his medical practice, he was a close colleague of long-serving MP Dr. R.J. Manion.

Earlier Dean family members lived in Hamilton County and in and near Brighton, Ontario. Records of their lives, especially including financial and land documents, correspondence, and photographs, are also included in this fonds, having been collected and passed down within the family.

The first series of this fonds consists of genealogical research material, including publications and correspondence. The rest of the fonds is organized roughly by generation within the Dean family; however, files were not split, so many generations may be reflected within a single file.