The Nez Perce have a long history dealing with the Americans but in the aftermath of the Whitman Massacre, their world is divided between cultures. Joseph is born with a foot in each world. How will he and his people react to the incoming Americans? 

Sources

Thunder in the Mountains by Daniel Sharfstein 

Chief Joseph & Flight of the Nez Perce by Kent Nerburn

Bury My Heart at Wounded Knee by Dee Brown

https://ww2020.net/history-websites/walla-walla-treaty-council-of-1855/

Walla Walla Treaty Councils: 1855 Walla Walla Treaty Council

https://www.historylink.org/File/5314

Political Elements of Nez Perce history during mid-1800s & War of 1877 by Stan Hoggatt (archive.org)

https://treaties.okstate.edu/treaties/treaty-with-the-nez-perces-1863-0843

Treaty of 1863 - Nez Perce National Historical Park (U.S. National Park Service) (nps.gov)