The series of events that led the Columbia Plateau Tribes to be forced out of their homelands and onto reservations was long and sorrowful. The beginning of white colonization and Native American resettlement in the northwest is often marked by the 1805 Lewis & Clark expedition and their first contact with Middle Columbia Salish Tribes. But data show that the impacts of Euro-American contact had already reached the Northwest by the early 1700s, when smallpox began to reduce the Plateau populations by the thousands (Hart, p. 35). By the time Americans began moving west in large numbers, the indigenous populations had already been decimated by half. 

Knowledge brought back to the East Coast by Lewis and Clark triggered a surge in American and Canadian fur companies' movement into Interior Salish territory (Hart, p. 37). The Native peoples were integral to the Northwest fur economy. They traded food like salmon, berries, and roots with the fur hunters, as well as the furs themselves, which they were often more adept at trapping. They helped early traders and settlers forge river crossings, build structures, and survive. The Native peoples valued their relationships with the trappers and traded for material objects, including guns, which had become a necessity for hunting as their diminishing population could no longer support traditional group hunts (Hart, p. 38-39). 

Euro-American settlement continued and in 1848 the lands inhabited by the Columbia Plateau Salish people for thousands of years were officially designed "Oregon Territory" by the United States government. Five years later, Congress divided the northern half into "Washington Territory" and formally recognized the rights of indigenous people, although the U.S. would soon after reverse those policies and enact new ones in their attempt to extinguish native culture and lifestyles (Hart, p. 43). 

With the establishment of Washington Territory came its first Territorial Governor Isaac Stevens, who was also appointed Superintendent of Indian Affairs by President Franklin Pierce. Stevens immediately set out to facilitate settlement onto tribal lands. Through controversial treaties, Stevens acquired more than sixty-four million acres of Northwest tribal land (Hart, p. 45). Before Stevens came to the east side of the North Cascades, ethnologist Gordon Gibbs reported to Stevens that he believed it “impractical to remove Indians in Washington Territory to a single reservation in the interior where they could all find food” - and that the Columbia Plateau tribes should be left alone, that white Americans would need to “learn how to live with the inconvenience” (Hart, p. 48). In spite of Gibbs' advice, Stevens continued making arrangements for treaty negotiations in Walla Walla in May of 1855. After many days of debate and much resistance, the Treaty of 1855 was signed by 14 bands of native people. It established the Yakama Reservation, the Umatilla Reservation, and the Wenatchee Fisheries Reservation. Allegedly, the tribes also agreed to cede a huge area “from the Cascade Mountains in the west to the Palouse in the east, and the Columbia and Snake Rivers in the south to the Methow and Columbia river drainages in the north” (Hart, p. 56). There is no evidence that the Methow were in Walla Walla in 1855, or that they signed the treaty. Yet, the Methow were held to the terms of the treaty which reduced their rights to their traditional lands, and removed them to the reservation.