The geography of New York (state) varies widely. Most of New York is dominated by farms, forests, rivers, mountains, and lakes. New York's Adirondack Park is larger than any U.S. National Park in the contiguous United States. Niagara Falls, on the Niagara River as it flows from Lake Erie to Lake Ontario, is a popular attraction. The Hudson River begins near Lake Tear of the Clouds and flows south through the eastern part of the state without draining lakes George or Champlain. Lake George empties at its north end into Lake Champlain, whose northern end extends into Canada, where it drains into the Richelieu River and then the St. Lawrence. Four of New York City's five boroughs are on the three islands at the mouth of the Hudson River: Manhattan Island, Staten Island, and Brooklyn and Queens on Long Island. "Upstate" is a common term for New York counties north of suburban Westchester, Rockland and Dutchess counties. Upstate New York typically includes the Catskill Mountains or areas North of the Catskill Mountains, the Capital district, The Adirondacks, the Erie Canal, Lake Champlain, Otsego Lake, Oneida Lake; rivers such as the Delaware, Genesee, Mohawk, and Susquehanna. The highest elevation in New York is Mount Marcy of the Adirondack Mountains. New York is the 27th-largest state. Location and size New York is located in the northeastern United States, in the Mid-Atlantic Census Bureau division. New York covers an area of 54,556 square miles (141,299 km2) making it the 27th largest state by total area (but 30th by land area). The state borders six U.S. states: Pennsylvania and New Jersey to the south, and Connecticut, Rhode Island (across Long Island Sound), Massachusetts, and Vermont to the east. New York also borders the Canadian provinces of Ontario and Quebec to the north. Additionally, New York touches the Atlantic Ocean to the southeast, and two of the Great Lakes: Lake Erie to the west and Lake Ontario to the northwest. Geology New York is part of the Marcellus Shale, a gas-rich rock formation which also extends across Ohio, Pennsylvania and West Virginia. Topography New York lies upon the portion of the Appalachian Mountains where the mountains generally assume the character of hills and finally sink to a level of the lowlands that surround the great depression filled by Lake Ontario and the St. Lawrence River. Three distinct mountain masses can be identified in the state.