Blackfoot River
https://en.wikipedia.org/wiki/...ver_Runs_Through_It_(film)
Clip from the article.
Filming[edit]
Although both the book and movie are set in Missoula and on the Blackfoot River, it was filmed in late June, early July 1991 in south central Montana in Livingston and Bozeman,[2] and on the nearby upper Yellowstone, Gallatin, and Boulder Rivers. The waterfall shown is Granite Falls in Wyoming.[3][4] Filming was completed in early September 1991.