At the age of 20, having spent 3 years attending medical classes at the University of Glasgow, Tolmie qualified as a Licentiate of the Faculty of Physicians and Surgeons of Glasgow, after which he joined the Hudson's Bay Company and soon sailed for the Pacific Northwest. In the spring of 1833 he arrived at Fort Vancouver. Soon after arriving he was sent to the proposed site for Fort Nisqually, at the southern end of Puget Sound near the Nisqually River delta. The route was via canoe up the Cowlitz River then overland by horse. Tolmie's journal provides the first detailed account of this route, today essentially that of Interstate 5.