Though US-93 swings to the southeast from Challis, the original alignment, now Hwy-75, winds west into the mountains through the 2,000-foot-deep canyon carved by the Salmon River. You’re deep in the forest by the time you reach Clayton (pop. 26), a riverside wide spot with a gas station and a biker-friendly tavern. Farther west, some 50 miles upstream from Challis, you come to the small but pleasant year-round resort of Sunbeam, which overlooks the confluence of the Yankee Fork and Salmon Rivers. There’s a café and campground at the junction, and just a half mile upstream you’ll find the area’s greatest attraction: the natural hot springs, steaming wildly on cold days and forming rock pools of varying temperatures in the Salmon River, marked by a stone bathhouse built during the New Deal 1930s but no longer in use.

  From Sunbeam, it’s only another 15 miles to Stanley, heart of the glorious Sawtooth mountains.