The St. Lawrence River runs along the border between Canada and the United States and is the defining feature of the Thousand Islands region. Near Thousand Islands National Park, the river spreads into a maze of more than 1,800 islands scattered across clear blue water. The river has long been an important travel and trade route, used for centuries by Indigenous communities and later by European explorers. Today, it’s a popular place for boating, paddling, and taking in the unique scenery of the Thousand Islands.