 About from its mouth the Hudson breaks through the rocky barrier of the highlands, forming the most easterly of the Appalachian Mountain ranges; and along its lower course it is bordered on the west by a nearly perpendicular wall of basaltic rock high, known as The Palisades.Above Troy, the Hudson receives the Hoosic River from the east and the Mohawk River from the west.The former stream rises in western Massachusetts and Vermont, and the latter near the center of New York.