The series contains photographs, textual records, and original artwork spanning the period 1710-1904, predominantly 1880-1903, related to the personal lives and interests of William McLennan and his family, including interests in family and Canadian history. Additionally, a sub-series contains records related to William McLennan’s work as a writer from the 1880s-1903.

Materials include full and partial drafts of published and unpublished articles, short stories, novels, and non-fiction works; research and reference materials; incoming and outgoing correspondence; legal and official documents; collected historical materials and documents; notes; sketches and a sketchbook; journals; newspaper clippings and ephemera; photographs; and other materials. Notable correspondents include Gustavus George Stuart, Marion Paterson McLennan, William Durie McLennan, Edward William Thomson, Pemberton Paterson, John Stewart McLennan, Francis McLennan, Bartlett McLennan, Neil Stewart, Hugh McLennan, William Kingsford, and the Royal Society of Canada, among others. Legal and official documents include copies of wills, notarial exams, and a certification of graduation.

Collected historical materials include ephemeral materials such as plates of historical figures and plans of famous battle locations, as well as tracings of famous Canadian autographs, bookplates, and reproductions of historical documents. Many of the original historical documents are related to the McLennan and Stewart families, including correspondence, business and financial documents, and ephemera related to Neil Stewart (1793-1881) and legal and financial documents related to John McLennan (1789-1866). The historical documents related to John McLennan are primarily agreements for land sales in Glengarry County, Ontario, where McLennan was a conveyancer. Other historical documents do not appear to have any particular connection to the McLennan family but may have been collected out of general historical interest. These documents include correspondence, loan agreements, commissions, land grants, letters patent, and a journal / memoranda book. While many of the documents relate to individuals of limited historical importance, others are related to more notable historical subjects including François Desjordy Moreau de Cabanac, Sir John Johnson, Joseph-Maurice Lamothe, Francis Baby, Jenkins Williams, Herman Witsius Ryland, Pierre-Amable De Bonne, John Mure, William Bacheler Coltman, John Stewart, John Gray, and Thomas Dunn.

File contains correspondence from William McLennan to daughter Alice (Patty) and correspondence from the Royal Society of Canada to William McLennan regarding his election.

File contains a journal kept by William McLennan for his son William Durie McLennan documenting travels across the Atlantic and in England, Italy, and Spain. The journal includes pasted in postcards, newspaper clippings, and original watercolours and sketches.

File contains a document certifying the authenticity of a watch owned by James Hanna and purchased by William McLennan, as well as a letter containing a French translation of Robert Burns' "John Anderson, my Jo."

File contains obituaries and remembrances of William McLennan in the "Daily Witness," the Montreal "Gazette," and "Harper's Weekly."

Portrait of William McLennan standing, reading a document with a monocle or magnifying lens.

Portrait of William McLennan seated, with a monocle in his right hand and an open document on his lap.

File contains a sketchbook with sketches and drawings in pen and ink, watercolour, and pencil of landscapes and architecture in Canada, the United States, and Europe.

The sub-series consists of textual records related to William McLennan’s work as a writer from the 1880s-1903. The series includes full and partial drafts of published and unpublished articles, short stories, novels, and non-fiction works; research and reference materials; incoming correspondence; and other materials. Writings are primarily about Montreal, including its history, physical environment, and historical figures. Historical figures treated include Raphael-Lambert Closse, Bénigne Basset, François Dollier de Casson, George Hardy, Pehr Kalm, Medar Jalot, Louis Juchereau de Saint-Denis, Richard Hamilton, Louis de Montéléon, Marie-Anne-Josette L’Estringant de Saint-Martin, Jean-Baptiste Migeon de Branssat, Daniel Greysolon Dulhut, Benedict XIII, Octave Crémazie, James Johnstone, and John McDonell. Research and reference materials include notes from historical sources, character sketches and timelines, and copies of archival documents, as well as original historical documents. Among the historical documents, the series includes a copy of Daniel Greysolon Dulhut's will and testament dated 1710 and signed by Dulhut. Correspondence relates to the writing, research, and publication of McLennan’s works. Notable correspondents include Jean Newton McIlwraith, co-author of "The Span o’ Life: A Tale of Louisbourg and Quebec," historian Joseph-Edmond Roy, archivist Douglas Brymner, journalist and historian Ernest Myrand, and John S. McLennan, among others.

File contains a letter to Neil Stewart; sketches and poems to William McLennan's children; incoming and outgoing correspondence; William McLennan and Marion Paterson's marriage certificate; photographs; drafts of writings and research notes; newspaper clippings; and diary pages.