Champlain Valley southward into the Valley of Vermont. The Vermont Lowlands are primarily underlain by sedimentary rocks, especially limestone and shale, though metamorphic rocks such as marble and slate are also present. Lake Champlain is situated in the Champlain Valley between the Green Mountains of Vermont and the Adirondack Mountains of New York, drained northward by the Richelieu River into the St. Lawrence River at Sorel-Tracy, Quebec (northeast of Montreal). Major tributaries of Lake Champlain include Otter Creek and the Winooski, Missisquoi, and Lamoille rivers in Vermont, and the Ausable, Chazy, Boquet, and Saranac rivers in New York. Lake Champlain also receives
Lake Champlain 'door of the country' or 'lake to the country'. The lake is an important eastern gateway to Iroquois Confederacy lands. The lake was named after the French explorer Samuel de Champlain, who encountered it in July 1609. While the ports of Burlington, Vermont, Port Henry, New York, and Plattsburgh, New York today are primarily used by small craft, ferries, and lake cruise ships, they were of substantial commercial and military importance in the 18th and 19th centuries. New France allocated concessions all along lake Champlain to French settlers and built forts to defend the waterways. In colonial times, Lake Champlain