The Fort Henry Historic Byway links sites tied to the region’s exploration, industry, landscape, and conflict. In 1810-1811, Andrew Henry led the Henry Expedition in the area as field captain of the St. Louis, Missouri Fur Co., and in 1811 Wilson Price Hunt named the post Fort Henry and the river Henry's Fork. From 1904 to 1914, the Fremont County Sugar Company slicer extracted sugar juice for pumping to Sugar City for purification, reflecting the hard labor of harvesting sugar beets with horses, wagons, and hand labor. The St. Anthony Sand Dunes extend about 15 miles, include dunes reaching 500 feet, and form part of the Sand Mountain Wilderness study area and surrounding sage and juniper lands that serve as winter range for deer and elk while also supporting recreation. The Clark County Civil Defense Cave is a 700-foot-long lava tube 35 feet below the surface, with evidence that buffalo, Indians, and perhaps mountain men used it for refuge. The Spencer Rock House, built by C.W. Hardy of Wood Live Stock Co. Limited, is a fieldstone house designed to use a natural spring in the basement as a cooling system, and the company grazed livestock in the Centennial and Beaverhead Mountains from 1895 until 1934. Near Spencer, an opal deposit was discovered after two deer hunters lost in fog noticed opal nodules, and the Spencer opal mine became the only mine open to the public for rock digging. On August 19, 1877, during the Nez Perce flight, General Howard camped on the east side of Camas Meadows; Nez Perce warriors stole mules and some horses before dawn, pursued cavalry fought beyond a timbered lava ridge, Captains Carr and Jackson withdrew after about 20 minutes, and Captain Norwood’s 35 men took cover behind a small lava ridge and built basalt breastworks that remain visible.