The Fall River is the largest Henrys Fork tributary. The river was referred to as the Falls River by trappers and prospectors in the early 1800’s and was historically named the Falls River in 1872 by the Hayden Geological Survey. However, in 1997 the name was changed to Fall River at the request of Idaho authorities. The Fall River begins on the Madison and Pitchstone Plateau in the southwest corner of Yellowstone Park. From there, the river flows 64 miles to its confluence with the Henry’s Fork of the Snake River near Warm River, Idaho. The river is largely inaccessible by road.
Fall River has good fishing for rainbow and cutthroat trout, and they get larger the higher upstream you go. The long hike and off-trail access minimize fishing pressure. However, there are many places to access the lower river.
Because of its easy access, the Cave Falls area sees the most fishing. The trout average 10 inches in this stretch and the action is good. These streams produce big trout although in the past few decades' brook trout have reached these waters.