For the Nez Perce, check out <em>Noon Nee-Me-Poo - Volume 1</em> by Allen P. Slickpoo, Sr.; Deward E. Walker, Jr. The words come straight from Nez Perce elders and speak on our origin.
In addition to what /u/retarredroof mentioned, two other books that would probably answer your question for you are:
The description says:
>A direct descendant of the immediate postcontact generation of Coast Salish in Washington State, Hillaire combines in her narrative life experiences, Lummi oral traditions preserved and passed on to her, and the written record of relationships between the United States and the indigenous peoples of the Northwest Coast to tell the story of settlers, government officials, treaties, reservations, and the colonial relationship between Coast Salish and the white newcomers.
I don't own the book, but I've read excerpts from it and I find it to be very compelling, particularly if one is aware of other oral traditions of other Pacific Northwest Coastal Tribes.
The other book is <em>Noon Nee-Me-Poo (We, the Nez Perces) Culture and History of the Nez Perces Volume One</em> by Allen Slickpoo, Sr. and Deward Walker.
This book is more of a precious one to me (despite being available on Amazon...) because it was produced by my Tribe, the Nez Perce, and contains knowledge from times before European colonization that was collected from elders and stories of the Tribe.