I would pick the Snake River somewhere between Wyoming, Idaho and Oregon. Why because it is overlooked to some extent by other trout rivers in Wyoming and Montana and offers the angler lots of species of both warm and cold river fish. I have caught cuttthroats over 4 lbs, channel cats, crappie, carp, whitefish to name less than half the species in that river. Verity would insure lack of boredom.
Tim