Sarnia is a city in Southwestern Ontario, Canada, and had a 2016 population of 71,594. It is the largest city on Lake Huron and in Lambton County. Sarnia is located on the eastern bank of the junction between the Upper and Lower Great Lakes where Lake Huron flows into the St. Clair River, which forms the Canada–United States border, directly across from Port Huron, Michigan. The site's natural harbour first attracted the French explorer La Salle. He named the site "The Rapids" on 23 August 1679, when he had horses and men pull his 45-ton barque Le Griffon north against the nearly four-knot current of the St. Clair River.