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 as late as the 1960s, but rejected for various reasons. The lake is also part of the 740-mile Northern Forest Canoe Trail, which begins in Old Forge, New York, and ends in Fort Kent, Maine. Burlington, Vermont (pop. 42,217, 2010 Census) is the largest city on the lake. The 2nd and 3rd most populated cities/towns are Plattsburgh, New York, and South Burlington, Vermont, respectively. The fourth-largest community is the town of Colchester. Lake Champlain contains roughly 80 islands, three of which comprise four entire Vermont towns (most of Grand Isle County). The largest islands: All active navigational aids on the