After a year of struggling against the Missouri, Lewis located the mighty river’s westernmost source, a slender spring-fed stream: “Judge then of the pleasure I felt in allying my thirst with this pure and ice cold water.” He had reached the Continental Divide, the elevated boundary separating rivers that run to opposite sides of the continent. From here on, rivers would flow west. The current would finally be with the Corps!

He climbed on, anticipating the view from the top: the prairies, the great river rolling to the western sea. Instead: “immence ranges...still to the West.” Here Jefferson’s shortcut to the Pacific was rendered as mythical as a mountain of salt. Lewis and Clark would be near starvation by the time they stumbled out of these mountains, six weeks later.