In 1805, the Corps of Discovery, led by Meriwether Lewis and William Clark and aided by Sacajawea of the Shoshone Native American tribe, crossed the Bitterroot Range several times. Lewis first crossed the mountains at Lemhi Pass on August 12, then returned across the pass to meet Clark. The entire expedition then crossed the pass to the Salmon River valley, and the next month entered the Bitterroot Valley from the south via either Lost Trail Pass or Chief Joseph Pass. It then crossed Lolo Pass to the west. The mountains were crossed by the Chicago, Milwaukee, St. Paul and Pacific Railroad (the Milwaukee Road).