The Thousand Islands are a 1,864-island North American archipelago that straddles the Canada–US border in the Saint Lawrence River as it rises from Lake Ontario’s northeast corner. They are about 50 miles (80 kilometers) downstream of Kingston, Ontario. The Canadian islands are located in Ontario, while the US islands are located in the state of New York.
The islands vary in size from over 40 square miles (100 square kilometers) to smaller islands with a single residence or uninhabited rocky outcroppings. Emergent land within the river channel must have at least one square foot (0.093 m2) of land above water level year-round and support at least two living trees to be considered one of the Thousand Islands.