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 been connected to the Erie Canal via the Champlain Canal since the canal's official opening September 9, 1823, the same day as the opening of the Erie Canal from Rochester on Lake Ontario to Albany. It connects to the St. Lawrence River via the Richelieu River, with the Chambly Canal bypassing rapids on the river since 1843. Together with these waterways the lake is part of the Lakes to Locks Passage. The Lake Champlain Seaway, a project to use the lake to bring ocean-going ships from New York City to Montreal, was proposed in the late 19th century and considered