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
Ten Thousand Islands at the northern end of the Ten Thousand Islands was occupied year-round 3,500 years ago, and other sites are presumed to have been inundated by a rise in sea level. The material culture of the Indians living in the Ten Thousand Islands was distinctive enough to be classified as, at least, a sub-area of the Glades culture area. Almost all of the Ten Thousand Islands are currently uninhabited. The largest, Chokoloskee Island, which is connected to Everglades City by a causeway, has about 400 permanent residents. Other islands have been sporadically inhabited in the 19th and 20th centuries by individuals