 It is the westernmost of the major notches through the White Mountains (the others being Franconia Notch, Crawford Notch, and Pinkham Notch).To the southeast, the valley of the notch is drained by the Lost River, leading to the Pemigewasset River, and ultimately the Merrimack, flowing into the Gulf of Maine.The northwest half of the notch is drained by Beaver Brook and the Wild Ammonoosuc River, part of the Connecticut River watershed leading to Long Island Sound.