The Nez Perce territory at the time of Lewis and Clark (1804-1806) was approximately and covered parts of present-day Washington, Oregon, Montana, and Idaho, in an area surrounding the Snake (Weyikespe), Grande Ronde River, Salmon (Naco'x kuus) (Chinook salmon Water) and the Clearwater (Koos-Kai-Kai) (Clear Water) rivers. The tribal area extended from the Bitterroots in the east (the door to the Northwestern Plains of Montana) to the Blue Mountains in the west between latitudes 45°N and 47°N.