A tributary of the Lower Clark Fork River system, the East Fork of the Bull River forms below the jagged peaks of the Cabinet Mountains Wilderness Area on the far northwestern edge of Montana. It drops west through alpine backcountry 8 miles to confluence with the Bull River. The East Fork supports resident trout populations and provides spawning and nursery habitat for cutthroat, bull, and brown trout from Cabinet Gorge Reservoir on the Clark Fork River.