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
Champlain Valley water from Lake George via the La Chute River Champlain Valley The Champlain Valley is a region of the United States around Lake Champlain in Vermont and New York extending north slightly into Quebec, Canada. It is part of the St. Lawrence River drainage basin, drained northward by the Richelieu River into the St. Lawrence at Sorel-Tracy, Quebec (northeast of Montreal). The Richelieu valley is not generally referred to as part of the Champlain Valley. The Champlain Lake Valley is the most heavily populated region in Vermont, broadly stretching eastward from the lake's shore to the base of the Green