Washington County, New York is part of the Great Appalachian Valley (also known simply as the 'Great Valley') which is a long narrow valley strip often between tall mountain ranges. The county transitions from the Taconic Mountains to the Adirondack Mountains, and from the Lake Champlain Valley to Hudson River Valley. Much of the county is part of the slate valley of the Upper Taconic Mountains (Taghkanic, meaning 'in the trees'). The eastern boundary of Washington County is the New York–Vermont border, part of which is Lake Champlain. This is also the border with New England proper. The northern end of the county is
Lake Champlain Lake Champlain Lake Champlain (French: Lac Champlain) (Abenaki: Pitawbagok) (Mohawk: Kaniatarakwà:ronte) is a natural freshwater lake in North America mainly within the borders of the United States (in the states of Vermont and New York) 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 facilities in the park and along the relatively undeveloped coastline of Lake Champlain. The cities of Plattsburgh, New York and Burlington,