These McGill papers are entirely concerned with his property and estate. They comprise legal documents and copies of letters (some in McGill's hand) concerning his land holdings on St. Paul St., Montréal, in Stanbridge, and in Detroit. McGill's cash book, 1809-1815, and copy by W.D. Lighthall of a deed of conveyance to McGill of some land formerly occupied by the city fortifications, 1805, are also included, as is a blue-print and sketch by W.D. Lighthall of the site of McGill's St. Paul St. house. Estate papers comprise a probate of McGill's will, copied by Alice Lighthall, and his executor's cash book.

The fonds reflects the scientific and literary outreach activities of the Montreal Natural History Society over the course of its existence and contains correspondence, minutes, financial records, council and committee reports, membership lists, donation lists, catalogues of holdings, newspaper clippings, lecture advertisements and weather maps. In addition, the fonds includes reference material to other societies and information regarding the publication and creation of the Canadian Naturalist and Quarterly Journal of Science, Canadian Naturalist and Geologist and the Canadian Record of Science.

The fonds is composed of the following series: 1) Accounting Records (1860-1917); 2) Administrative Records (1833-1887); 3) Catalogues (ca.1829-ca.1925); 4) Correspondence (1871-1896 with gaps); 5) Essays and Lectures (1829-1852); 6) Minutes (1827-1832,1844-1923); 7) Montreal Microscopical Society (1884-1906); 8) Reports (1828-1881 with gaps); 9) Weather Maps (1895-1897).