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 of Two Mountains Lake of Two Mountains Lake of Two Mountains (French: Lac des Deux Montagnes) is part of the river delta widening of the Ottawa River in Quebec, Canada, at its confluence with the St. Lawrence River. Lake of Two Mountains has four outflows: Rivière des Mille Îles and Rivière des Prairies, bordering Île Jésus, and two branches of the Ottawa River, flowing into the St. Lawrence via Lake Saint-Louis, on either side of Île Perrot. The city of Deux-Montagnes is located on the lake's north shore, where it flows into Rivière des Mille Îles. The southwest portion of the city of