St. Lawrence County is a county in the U.S. state of New York. As of the 2020 census, the population was 108,505. The county seat is Canton. The county is named for the Saint Lawrence River. This was as named by early French explorer Jacques Cartier for the Christian saint Lawrence of Rome, as he visited the river on the saint's feast day. The county is part of the North Country region of the state. St. Lawrence County comprises the Ogdensburg-Massena, NY Micropolitan Statistical Area and is New York's largest county by area.