Lake Champlain /ʃæmˈpleɪn/ is a natural freshwater lake in North America mainly within the borders of the United States but partially situated across the Canada–U. S. Border, in the Canadian province of Quebec, the New York portion of the Champlain Valley includes the eastern portions of Clinton County and Essex County. Most of this area is part of the Adirondack Park, there are recreational opportunities in the park and along the relatively undeveloped coastline of Lake Champlain. The cities of Plattsburgh, New York and Burlington, Vermont are on the western and eastern shores, respectively. The Quebec portion is in the county municipalities of Le Haut-Richelieu. There are a number of islands in the lake, the largest include Grand Isle, Isle La Motte, and North Hero, all part of Grand Isle County, Vermont. The Champlain Valley is the northernmost unit of a system known as the Great Appalachian Valley. The Champlain Valley is a section of the larger Saint Lawrence Valley. Lake Champlain is one of large lakes scattered in an arc through Labrador, in Canada, the northern United States. Although it is smaller than each of the Great Lakes, Lake Champlain is a body of fresh water. Approximately 1,269 km2 in area, the lake is roughly 201 km long and 23 km across at its widest point, the lake varies seasonally from about 95 to 100 ft above mean sea level. Lake Champlain drains nearly half of Vermont, and approximately 250,000 people get their water from the lake. The lake is fed in Vermont by the LaPlatte, Lamoille, Missisquoi, Poultney, and Winooski rivers, along with Lewis Creek, Little Otter Creek, and Otter Creek. In New York, it is fed by the Ausable, Boquet, Great Chazy, La Chute, Little Ausable, Little Chazy, Salmon, in Quebec, it is fed by the Pike River. It is connected to the Hudson River by the Champlain Canal, parts of the lake freeze each winter, and in some winters the entire lake surface freezes, referred to as closing. In July and August, the temperature reaches an average of 70 °F. The Chazy Reef is an extensive Ordovician carbonate rock formation extends from Tennessee to Quebec. It occurs in prominent outcropping at Goodsell Ridge, Isle La Motte, the oldest reefs are around The Head of the south end of the island, slightly younger reefs are found at the Fisk Quarry, and the youngest are in fields to the north
Lake Champlain in Burlington Harbor during late-May 2012 sunset
Map of Lac Champlain, from Fort de Chambly up to Fort St-Fréderic in Nouvelle France. Cadastral map showing concessions and seigneuries on the coasts of the lake according to 1739 surveying.