The French built the fort in 1691 as a trading post on the lower Saint Joseph River. It was located where one branch of the Old Sauk Trail, a major east-west Native American trail, and the north-south Grand River Trail meet; together the combined trail fords the river. The fort was a significant stronghold of the fur trade at the southern end of Lake Michigan. Prior to the French and Indian War (the North American front of the Seven Years' War in Europe), the post had a French garrison of 10 soldiers, a commandant, blacksmith, Catholic priest, interpreter, and 15 additional households.