The Hellmuth Wolff Organ Collection consists primarily of organ plans, pamphlets, photographs, books and periodicals, and personal correspondence. The majority of these documents are associated with or represent one of the fifty organs in Wolff’s opus. In addition to depicting Wolff’s instruments, the collection of organ plans also includes Wolff’s drawings for proposed but not-constructed organs, plans by other organ builders, and plans drawn by Wolff that are based on historical models and treatises by writers such as Dom Bédos. Of the photographs, most are associated with specific Wolff organ projects and represent a span date of the late 1960s to the early 2000s. Also in the photograph collection are images of historical organs in Europe, which Wolff presumably used in modelling and designing several of his instruments, as well as images associated with other organ projects by builders such as Casavant Frères, Karl Wilhelm, and Rieger, all of whom Wolff worked with before establishing his own workshop in Laval. The collection of pamphlets includes programs, program notes, and concert series information for several of the Recitals and concerts performed on Wolff’s instruments. Of the periodicals and books, titles include The American Organist, Choir & Organ, and Orgelforum. Also in the collection are several three-dimensional models, or maquettes, of Wolff organs.

Three letters from Seaton relating to the Rebellion of 1837, including a letter to General Fitzroy Sommerset about the capture of St-Eustache.

Collection consists of 36 autograph letters written to James Cameron and his son Archie. The correspondence includes letters by friends, associates, and members of the Cameron family in Toronto, Lake Beauport, Scotland, England, Hull, and Montreal. Subjects include family news, freemasonry, business (regarding deed of sales), factory work in Toronto, curling, and an April Fools' Day letter. With three extant envelopes.

The collection consists of autographed signed letters from multiple senders, representing authors, artists, politicians, and other figures from Canada and Europe. The letters were accumulated by the Rare Books and Special Collections unit of the McGill Library over many years and assembled into the collection.

Consists of an English translation of a letter to the Marquis de la Jonquière written by Antoine-Louis Rouillé, comte de Jouy, secretary of state for the French Navy, at Versailles, dated 28 February 1750. The letter discusses an immediate release of prisoners of war taken during conflicts between the French and British colonies. It also includes a mention of Indigenous allies of England and France, and Indigenous people captured during the conflicts: "the Indian Prisoners among the two Nations be likewise released, but after all the French and English Prisoners are released" The letter also includes the name of examiner Josiah Willard, secretary of the province of Massachusetts-Bay.

Letters and diaries, including typescript transcriptions with photographs, newspaper clippings and ephemera.

This collection consists of translations from Terence, begun in 1778, and correspondence on military, political and private matters, 1787-1821, mostly addressed to Thomas Coutts, banker.

Collection of correspondence between the years 1818 and 1828, predominantly on the matters of The Society of Antiquaries of London, addressed to Daniel Lysons, a British antiquarian and topographer. Comprises 25 letters mounted on paper. The first letter of September 5, 1818, is addressed to Samuel Lysons (1763-1818).

This collection reflects Henry S. Chapman's relationships with a number of important figures in Montreal's political and business history, between roughly 1833 and 1853, the period following Chapman's return to London. A significant amount of the material in this collection is related to the 1837-1838 Upper and Lower Canada Rebellions (especially in Montreal), as well as events occurring immediately after the uprisings.

Consists of copies of original material, chiefly correspondence, arranged roughly by date. The contents of letters (1835-1853) include business partnerships, political reform, and personal news. Significant correspondents include Louis-Joseph Papineau, Louis-Hippolyte La Fontaine, Jacob Dewitt, François-Antoine Larocque (of Laroque and Bernard), Joseph Perreault, and Edmund Bailey O’Callaghan. There is also a partial manuscript on Canadian history and pages from a scrapbook, both dating from the 1830s.

This collection consists of contemporary copies of letters written by T. Blackwood from Michilimackinac to James and Andrew McGill & Co., to Ch. Chaboillez, and to T. and J. McGregor.