The West Branch of the Ausable arises from the conjunction of the MacIntyre, South Meadow and Marcy Brooks, east of Mount Jo near the Adirondak Loj; it then runs northeast to Au Sable Forks (), and is fed by Lake Placid and the Chubb River along the way. At high water-levels, the upper end provides demanding white-water paddling opportunities. Further along, it runs through High Falls Gorge at the Wilmington Notch, a gorge formed by a fault zone, with cliffs on one side and cliffs on the other.