Take US95 north to Boise and into the Idaho mountains. There's a scenic arc from McCall in the west to Salmon in the east. From Salmon you can take US93 north to Missoula and Glacier. Or SW to Idaho Falls and Tetons.
Eastern Oregon would also be on your way. NV140, OR205 takes you to Steens Mtn. Branching off of US95 north of Jordan Valley is gravel roads to Succor Creek, and Leslie Gulch, both with fascinating rock formations. And further north on both sides of the state border is Hells Canyon and mountains (Blues in Oregon).