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 from the British posts at the northern end of the lake. With the end of the Revolutionary War in 1783, the British naval fleet on Lake Champlain retreated up to St. John’s. However, British troops garrisoned at Fort Dutchman's Point (North Hero, Vermont) and Fort au Fer (Champlain, New York) on Lake Champlain, did not leave until the 1796 Jay Treaty. Eager to take back control of Lake Champlain following the end of the Revolutionary War, Americans flocked to settle the Champlain Valley. Many individuals emigrated from Massachusetts and other New England colonies, such as Salmon Dutton, a settler of