After leaving their camp at Traveler’s Rest, the Corps of Discovery, led by captains Meriwether Lewis and William Clark encountered one of the most grueling stretches of their expedition. The Shoshones advised them against descending the Snake River to the Pacific Ocean, and so their alternate route necessitated going through a mountain pass farther north. Later named “Lolo Pass,” the mountain gap the Corps crossed aided their overall westward progress but inaugurated one of the most difficult parts of their journey. Over the course of eleven days, they experienced treacherous slopes and contours of the Bitteroot Mountains. Their Shoshone guide nicknamed “Old Toby” told them their travel through the mountains would take six days. This miscalculation was, oddly enough, due in part to his guiding the party down “a wrong road,” taking them “out of [their] rout 3 miles” before falling back into “the right road.” Nevertheless, the party crossed over Lolo Pass, the currently-demarcated border between Idaho and Montana on the Continental Divide. They passed several hot springs on their way through, stopping briefly to test (and even taste) the water, and discovered that it was “hot & not bad tasted.” After Lewis’s cohort caught up with Clark’s, they set up camp near Pack Creek, specifically on the lower end of Packer Meadows in Idaho County, Idaho.
Having successfully traversed the mountains (albeit with much difficulty), the party stepped off the Lolo Trail to enjoy the hospitality, food, and shelter of the Nez Perce tribe, located at Weippe Prairie. After encamping together, the Nez Perce informed the party of travelers that the trail the party took was an older trail the Nez Perce had been using to go east to hunt for deer and bison, as well as to procure horses and rendezvous with other tribes (sometimes with the unfortunate result of combating their enemies, losing tribespeople and horses in the process). Interestingly, the expedition members noticed signs of the trail and pass being used on the first day they set out to cross the Bitterroots, as they “passed a tree on which was a nomber of Shapes drawn on it with paint by the natives,” among other signs that they supposed to be “a place of worship among them [the Indians].” They also saw “pine trees pealed as far up as a man could reach,” assuming that the natives had done so to mix the inside bark of the trees with dried fruit to eat. They also posited that at the hot springs “one of the Indians had made a whole to bathe [in].” Before leaving the Nez Perce to sail on the Columbia River, the party learned that the Nez Perce “make great use of Swetting,” referring to the tribe’s use of “hot and cold baethes,” which were used to treat skin diseases on account of the supposed healing properties of hot springs’ water. On the return trip home, some expedition members and natives “amused themselves” by fully utilizing the springs near Lolo Pass, a welcome warmth and delight after “bid[ding] adieu to the snow” and remembering the hardships they had previously experienced in crossing the Rocky Mountains.