Grant, Campion and Company was one of the most important firms engaged in the fur trade to the southwest of Grand Portage (near Grand Portage, Minn.), Michilimackinac, and Detroit (Mich.) in the early 1790s. With Todd, McGill and Company, Forsyth, Richardson and Company, and Alexander Henry, the firm entered into negotiations with the North West Company concerning the allocation of trading zones, and in September 1792 the parties agreed not to prejudice one another’s interests. The partnership was dissolved in November 1795. Campion died soon after and Grant’s involvement in the fur trade ended.

George R. Grant was secretary and accountant to the Geological Survey of Canada. He was also an executor of Sir William Edmond Logan's estate.