From Wikipedia ...
Old Joseph was one of the first Nez Percé converts to Christianity and a vigorous advocate of the tribe's early peace with whites. In 1855 he aided Washington's territorial governor and set up a Nez Percé reservation that expanded from Oregon into Idaho. The Nez Perce agreed to give up a section of their tribal lands in return for an assurance whites would not intrude upon the sacred Wallowa Valley.
Nevertheless, in 1863, following a gold rush in Nez Percé territory, the federal government took back approximately 6 million acres (24,000 km2) of this land. That confined the Nez Percé to a 750,000-acre (3,000 km2) reservation in Idaho, which was only one tenth its previous size. Old Joseph argued that this second treaty was never approved by his people. Feeling deceived, Old Joseph condemned the United States, slashed his American flag, shred his Bible, and declined to move his band from the Wallowa Valley or to sign the treaty that would make the new reservation boundaries legitimate.