James McGill was educated at the University of Glasgow, and soon afterwards left for North America to explore the business opportunities there. By 1766, he was in Montreal, whose trade opportunities had recently been laid open following the British Conquest of New France. He entered the fur trade south of the Great Lakes, at first as a clerk or agent for the Quebec merchant, William Grant of St. Roch. By the next year, the firm of "James McGill & Co." was trading at Michilimackinac.