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
Champlain and St. Lawrence Railroad line. The line was extended south along the Richelieu River valley in 1851 to Rouses Point, New York and the following year saw a more direct routing built from the St. John-Laprairie line to St. Lambert, directly opposite Montreal to avoid the indirect journey up and down the St. Lawrence River from Laprairie. This latter line effectively reduced the line into Laprairie to branch line status and it would be later abandoned. The C&SL merged with the Montreal and New York Railroad in 1857, formerly known as the Montreal and Lachine Railroad, with the new company being named the Montreal