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 inspection stations on Heart Island and at Cape Vincent, NY, and Canada has seasonal vessel inspection stations at Rockport, Ontario and Gananoque, Ontario, and both Canada Border Services Agency (CBSA) and the U.S. Customs and Border Protection (CBP) will travel to selected ports and marinas to conduct inspections upon request. 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