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
Avalanche Lake (New York) miles to the east. Avalanche Lake feeds Lake Colden to the south, in the Hudson River watershed. To the north, the trail to the lake from the Adirondak Loj surmounts Avalanche Pass, which is only slightly above lake level but separates it from the Lake Champlain (St. Lawrence River) watershed. Following the lake toward Lake Colden, the trail is choked with large boulders, and a number of wooden ladders have been built to make passage possible. There are also three places where the trail takes to wooden catwalks, first built in the 1920s, that are bolted directly into the cliff