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 American portion of the lake are maintained by USCG Burlington station, along with those on international Lake Memphremagog to the east. Aids to navigation on the Canadian portion of the lake are maintained by the Canadian Coast Guard. There are a number of parks in the Lake Champlain region in both New York and Vermont. Those on the New York side of the lake include: Point Au Roche State Park, which park grounds have hiking and cross country skiing trails, and a public beach; and the Ausable Point State Park. The Cumberland Bay State Park is located on Cumberland Head,