 Grant became partners with Gabriel Cotté and Alexander Shaw.In 1791, he formed Grant, Campion and Company with Étienne-Charles Campion and Samuel Gerrard; the firm played an important role in the development of the fur trade in the region, becoming share-holders in the North West Company and coming to an agreement with that company regarding access to trading territories.In 1787, he married Marguerite Fafard, dit Laframboise, at Trois-Rivières.