The route back over the Bitterroots turned out to be almost as challenging as the previous crossing. They got lost and caught in deep snow, and had to return to the Nez Perse for help.
When they reached the Great Plains, they split into two parties. It was then that Clark's party named a rock by the river Pompey's Tower, and where Clark scratched his signature and the date – the only physical evidence of the expedition's existence on the whole epic journey.
