Adirondack Mountains or Adirondacks, group of mountains, northeastern New York State, bounded by the Canadian border on the north, the Mohawk River valley on the south, the St. Lawrence River and Black River valleys on the west, and the Lake Champlain area on the east. The Adirondacks are composed mainly of metamorphic and igneous rock, among the oldest in the world (see Precambrian time). Sometimes erroneously included in the Appalachian system, the Adirondacks are geologically related to the Canadian Shield and are generally considered a southern extension of it. About half of the total acreage of the Adirondack Mountain range is part of the New York State Forest Preserve. More than 405,000 hectares (2.4 million acres) of forest preserve land have been incorporated into Adirondack Park (created in 1892), where particular conservation and recreation efforts have been focused. The park, which has a total area of about 2 million hectares (6 million acres), more than half of which is privately held, occupies the central portion of the mountain range and is magnificently scenic. In the park is Mount Marcy (1,629 m/5,344 ft), the highest summit in the Adirondacks and in the state. Forty-five other peaks are more than 1,200 m (4,000 ft) high, among them Algonquin Peak (1,559 m/5,114 ft) and Skylight, Haystack, and Whiteface peaks. The region has hundreds of large and small lakes, notably Lakes Placid and George and Schroon, Cranberry, Upper and Lower Saranac, and Raquette lakes. The Hudson, Ausable, and Black rivers rise in the Adirondacks, and numerous streams cut through the mountains. Adirondack Park is thickly forested with spruce, pine, and hemlock and with some types of deciduous trees. Wildlife is abundant, although some of the larger species are diminishing in number. There are no large cities or major industrial zones here. The area is a popular all-year sport and resort region.