Two upland regions—the Adirondack Mountains and the Appalachian Highlands—dominate the topography of New York State.
The Adirondacks cover most of the northeast and occupy about one-fourth of the state's total area. The Appalachian Highlands, including the Catskill Mountains and Kittatinny Mountain Ridge (or Shawangunk Mountains), extend across the southern half of the state, from the Hudson River Valley to the basin of Lake Erie. Between these two upland regions, and also along the state's northern and eastern borders, lies a network of lowlands, including the Great Lakes Plain; the Hudson, Mohawk, Lake Champlain, and St. Lawrence valleys; and the coastal areas of New York City and Long Island.
The state's highest peaks are found in the Adirondacks: Mt. March, 5,344 feet (1,629 meters), and Algonquin Peak, 5,114 feet (1,559 meters). Nestled among the Adirondacks are many scenic lakes, including Lake Placid, Saranac Lake, and Lake George. The region is also the source of the Hudson and Ausable rivers. The Adirondack Forest Preserve covers much of this terrain, and both public and private lakes are mainly for recreational use.
The highest peak in the Catskills is Slide Mountain, at 4,204 feet (1,281 meters). Lesser upland regions of New York include the Hudson Highlands, projecting into the Hudson Valley; the Taconic Range, along the state's eastern border; and Tug Hill Plateau, set amid the lowlands just west of the Adirondacks.
Three lakes—Erie, Ontario, and Champlain—form part of the state's borders. The state has jurisdiction over 594 sq mi (1,538 sq km) of Lake Erie and 3,033 sq mi (7,855 sq km) of Lake Ontario. New York contains some 8,000 lakes; the largest lake wholly within the state is Oneida, about 22 mi (35 km) long, with a maximum width of 6 mi (10 km) and an area of 80 sq mi (207 sq km). Many smaller lakes are found in the Adirondacks and in the Finger Lakes region in west-central New York, renowned for its vineyards and great natural beauty. The 11 Finger Lakes themselves (including Owasco, Cayuga, Seneca, Keuka, Canadaigua, and Skaneateles) are long and narrow, fanning southward from a line that runs roughly from Syracuse westward to Geneseo.
New York's longest river is the Hudson, extending from the Adirondacks to New York Bay for a distance of 306 mi (492 km). The Mohawk River flows into the Hudson north of Albany. The major rivers of central and western New York State—the Black, Genesee, and Oswego—all flow into Lake Ontario. Rivers defining the state's borders are the St. Lawrence in the north, the Poultney in the east, the Delaware in the southeast, and the Niagara in the west. Along the Niagara River, Niagara Falls forms New York's most spectacular natural feature. The falls, with an estimated mean flow rate of more than 1,585,000 gallons (60,000 hectoliters) per second, are both a leading tourist attraction and a major source of hydroelectric power.
About 2 billion years ago, New York State was entirely covered by a body of water that periodically rose and fell. The Adirondacks and Hudson River Palisades were produced by undersea volcanic action during this Grenville period. At about the same time, the schist and other crystalline rock that lie beneath Manhattan were formed. The Catskills were worn down by erosion from what was once a high, level plain. Glaciers from the last Ice Age carved out the inland lakes and valleys and determined the surface features of Staten Island and Long Island.