The Snake River corridor in autumn 1811 was one of the most punishing environments on the continent.

The river dropped through a series of canyons, impassable by the boats the expedition had acquired, requiring portages over terrain that exhausted even the strongest men.

The Shoshone people of the region were in a position of considerable uncertainty regarding the expedition: unfamiliar strangers moving through their country in large numbers, with unclear intentions and limited shared language.

Food became scarce.

Horses had to be eaten.