This collection was compiled by the Oregon Historical Society from a variety of sources. It consists of papers of and about Hudson's Bay Company Chief Factor John McLoughlin and his family. People represented in the collection include members of McLoughlin's maternal family, the Frasers, and some of his descendants, who were members of the Rae, Harvey, Wygant, and Winch families through marriage and birth. Papers in the collection include correspondence, property and financial documents, scrapbooks, and biographical and genealogical materials. Papers of the McLoughlin, Fraser, Rae, and Harvey families are a mix of original documents, handwritten or typescript copies, photostatic reproductions, photocopies, and microfilm, while the Wygant and Winch papers are all original.

The McLoughlin and Fraser papers include correspondence of John McLoughlin; his uncles Simon Fraser and Alexander Fraser; his cousin John Fraser; his great-uncle Malcolm Fraser; his sister Marie-Louise McLoughlin (also named de Saint-Henri); and his sons John McLoughlin, Jr., and David McLoughlin. Some of the correspondence with and among the Fraser family is in French. John McLoughlin's correspondence includes communications with other officials in the Hudson's Bay Company, much of which is contained in two letterbooks, one original and another photocopied. David McLoughlin's papers include correspondence with Oregon Historical Society founder George H. Himes. Other papers of the John McLoughlin and Fraser families include property, estate, and financial documents of John McLoughlin; materials about McLoughlin's house in Oregon City, including specifications for its restoration in the 20th century by architect Glenn Stanton; a report by McLoughlin about Native peoples living between Fort William and Lake of the Woods in Canada; a 1775 land lease certificate in French, listing McLoughlin's great-uncle Malcolm Fraser and father John McLoughlin as witnesses; biographical and genealogical materials; and research by Burt Brown Barker.

The Rae and Harvey family papers consist of the wills of William Glen Rae and John Rae; marriage settlement agreements for Eloisa McLoughlin's marriages to William Glen Rae and to Daniel Harvey; a letter from Edward Roberts to Daniel Harvey; materials relating to Eloisa Rae Harvey's will; and materials about John McLoughlin that were compiled by Maria Louise Myrick (née Rae). Wygant family papers consist of Theodore Wygant's reminiscences about his overland emigration to Oregon; a lawsuit Theodore Wygant took part in against Forbes Barclay; a notebook and a scrapbook compiled by Maria Louise Wygant; and papers of Maria Louise Wygant's estate. Almost all the Winch family papers in the collection are property deeds and legal documents of Martin Winch. The exception is deeds for his son, Simeon Reed Winch, to property on Cornell Road in Portland, Oregon.