Madison River

The Madison River is a 183-mile (295 km) headwater tributary of the Missouri River, rising at Madison Junction in Yellowstone National Park, Wyoming, where the Firehole and Gibbon rivers converge. From the park the river flows west and then north through southwestern Montana before joining the Jefferson and Gallatin at Three Forks, Montana, to form the Missouri. The Madison's hydrology is heavily shaped by infrastructure. Hebgen Dam forms Hebgen Lake in Gallatin County; immediately downstream, the 1959 Hebgen Lake earthquake triggered a massive landslide that naturally dammed the river and created Quake Lake. Further north, Madison Dam in Madison County impounds Ennis Lake. These reservoirs together regulate flow, support recreation, and generate hydroelectric power throughout the watershed. The river's average discharge near Three Forks is 1,647 cu ft/s. The Madison is one of the most famous trout rivers in the United States and is classified as a blue-ribbon fishery by Montana. Brown trout, rainbow trout, cutthroat trout, and mountain whitefish populate its waters, while the surrounding valley supports grizzly bears, wolves, and other large fauna of the greater Yellowstone ecosystem.