These islands are the peaks of a former mountain range swallowed by the St. Lawrence River. They form a natural border stretching about 80 km between Canada and the United States.

The Thousand Islands archipelago comprises 1865 islands and islets. This select club does not include just any old rock pile! To be included, an isle must measure more than 1 m², have at least one tree or bush and be above water level year-round.