The Big Hole is a free-flowing (i.e., undammed) 156-mile long river, which is a tributary of the Jefferson River and part of the Upper Missouri River Watershed. Flanked by the Beaverhead, Pintlar, and Pioneer mountains, the Big Hole Valley is surrounded by vast wilderness, national forests, and several national scenic trails.
The Big Hole River supports a world-class trout fishery and is home to the last remnant population of fluvial (i.e., stream-dwelling) Arctic grayling. The Big Hole also supports populations of native westslope cutthroat trout. The Big Hole Basin is home to 47 animal and 79 plant species of concern, including: gray wolf, wolverine, grizzly bear, golden and bald eagles, greater sage-grouse, trumpeter swan, peregrine falcon, and whooping crane.