Thousand Islands level year-round, and support at least two living trees. The Thousand Islands archipelago is located at the outlet of Lake Ontario at the head of the Saint Lawrence River. The region is bisected by the Canada–United States border and covers portions of Jefferson and St. Lawrence counties in the U.S. state of New York, in addition to parts of the United Counties of Leeds and Grenville and Frontenac County in the Canadian province of Ontario. Geologically, most of the islands are located where a branch of the Canadian Shield runs south across the river to join with the Adirondacks. The
Thousand Islands Border Crossing Thousand Islands Border Crossing The Thousand Islands Border Crossing connects the towns of Alexandria Bay, New York and Ivy Lea, Ontario on the Canada–US border. The crossing is via the international span of the Thousand Islands Bridge. The Thousand Islands bridge, which was completed in 1938, is actually a system of three bridges and the island roadways connecting them. The international span, which crosses a small rift between Wellesley Island in the US and Hill Island in Canada, is only in length. A second, parallel span was built in 1959 to accommodate congestion at the ports of entry. The US