At Challis, our main route follows the 1940s alignment of US-93, heading west into the Sawtooth Mountains, but today’s US-93 swings southeast toward Arco and the Craters of the Moon National Monument through the Lost River Valley. The scenery here remains spectacular, with the mountains towering over the ranches of the valley floor, but it can’t compare with the glories of the old road route.

  But if you’re in a rush, or there’s been a recent storm blocking the mountain passes, or you just want to see another corner of Idaho, US-93 will be there for you. Mountaineers follow US-93 on their way to climb 12,662-foot Mt. Borah, the highest point in Idaho and a demanding though not technically difficult summit to reach. The trailhead is at the end of the well-signed Borah Peak Access road, roughly halfway between Challis and Mackay. For details, contact the USFS ranger station (208/588-2224) in Mackay.

  The rough and ready town of Mackay (pop. 575; rhymes with wacky) is the valley’s hub. You can stay at the Wagon Wheel (208/588-3331), where rooms with kitchenettes go for as little as $40 a night. Mackay also hosts an annual rodeo, the Custer County Fair, and a mountain bike race, but it’s best known for its famous free barbecue on the 3rd Saturday in September, when hundreds of people come here for general fun and games and massive amounts of free food (“Tons of Meat—Mackay’s Treat” say the signs).

  South of Mackay, US-93 continues to Arco, then elbows west through the eerie Craters of the Moon, rejoining Hwy-75 at Shoshone.