On July 12, 1806, Meriwether Lewis’s return detachment finished two canoes at the portage camp above the Great Falls. By mid-morning the craft were ready—just as the party discovered that ten of its best horses were missing and feared stolen.

Violent wind kept Lewis from crossing until late afternoon. When the gale eased, the men ferried baggage and meat, swam the remaining horses, and camped on the opposite shore under swarms of mosquitoes. Far to the south, Clark’s party fought its own crisis on the Jefferson.

The split expedition’s mid-July journals show Montana as the Corps’ hardest proving ground on the way home: rivers to remaster, horses to recover, and a country still full of risk.