 The watersheds divide at Triple Divide Peak in Glacier National Park.West of the divide, the Clark Fork of the Columbia (not to be confused with the Clarks Fork of the Yellowstone River) rises near Butte and flows northwest to Missoula, where it is joined by the Blackfoot River and Bitterroot River.Farther downstream, it is joined by the Flathead River before entering Idaho near Lake Pend Oreille.