Clearwater and Snake River National Recreation Trail is a 14 mile lightly trafficked loop trail located near Lewiston, ID that features a river and is good for all skill levels. The trail offers a number of activity options and is accessible from March until October.
I agree with Jim Cooper's comment below. Be sure to check out the Hell's Gate State Park website for better info.
The hiking we did within Hell's Gate State Park took us to some amazing rock formations, and being that I was there with a bunch of geologists, this was a big plus. I think we all expected a bit more of a "hike". Where there was mud alongside the river, things got a bit dicey. Other places, it was quite rocky and seemed more appropriate for adventures on wheels. The water levels were high when we visited, so our hike was cut short. A rattlesnake on the side of the trail at this point also made us feel a bit unwelcome (though that was exciting).
This is not a trail, it is a State Campground. There are trails around there but this does NOT help anyone find them