Because of its volcanic topography, Idaho has more dips and curves than most states. About the only straight roads in Idaho are its Interstates, Highway 26 west of Idaho Falls, and the road from Jerome to Sun Valley. The most scenic route, for my money, is the one through the Sawtooth National Recreation Area northwest of Ketchum.
You have no choice but to take your time and enjoy the scenery in most of Idaho. For example, if you decide to drive south from Orofino to Boise, plan to take most of a day. Shaped like a giant triangle, Idaho has a truly beautiful center full of high mountains and dipping curves to gape at and experience. Salmon is one of the most isolated towns in the United States, and Highway 93 which drifts south from it along the Salmon River is beyond beautiful if you choose Highway 75 at Challis. Drive cautiously because local wild animals often treat the centers of highways as their midday homes.
If you want to see what the pioneers experienced and get a glimpse of how Idaho was formed, go to Craters of the Moon National Monument and Preserve. Dress for heat and expect to walk a lot. If you so choose, this is an excellent area to explore this country’s development of atomic power. The facilities are around the town of Arco. One of the more scenic areas of Idaho that is often overlooked and decidedly curvy is altitude-challenging Highway 20 west of Yellowstone National Park. I once saw a farmer harvesting a wheat field prior to a big rain dump along this route that is forever a vivid memory among the best sights among my travel vistas.
Despite recent fires in southwest Washington and northern Oregon that made for hazardous breathing where I live, Idaho remains the only place where I saw helicopters actually dealing with a major forest fire. We fled the scene.