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
New York State Canal System Cayuga Lake to the Erie Canal; the Oswego Canal connects the Erie Canal to Lake Ontario; and the Champlain Canal connects the Hudson River to Lake Champlain. In 1903 New York State legislature authorized construction of the "New York State Barge Canal" as the "improvement of the Erie, the Oswego, the Champlain and the Cayuga and Seneca Canals". In 1905, construction of the Barge Canal began; it was completed in 1918, at a cost of $96.7 million. It opened to through traffic May 15, 1918. The Barge Canal's new route took advantage of rivers (such as the Mohawk River, Oswego