Southwest of West Yellowstone and north of Ashton, the Falls River flows from the southwestern quadrant of Yellowstone National Park and merges with the Henrys Fork of the Snake River. There are numerous waterfalls in the upper sections. Prior to human intervention, there were no fish in the upper reaches. But now you can expect to find plentiful trout. The best section of the river is probably from Mountain Ash Creek to the NFS Cave Falls Campground. The Upper Falls River is worth exploring to from Beula Lake to Mountain Ash Creek.
Many fly fishermen hit both the river and its many tributaries and nearby lakes, including Robinson Creek, Mountain Ash Creek, Horseshoe Lake, Grassy Lake, Beula Lake and Hering Lake.
Overall, Falls River is the 10th most popular fly fishing river of all 17 fly fishing spots in Idaho.