A number of wars occurred in the wake of the Oregon Treaty of 1846 and the creation of Oregon Territory and Washington Territory . Among the causes of conflict were a sudden immigration to the region and a series of gold rushes throughout the Pacific Northwest . The Whitman massacre of 1847 triggered the Cayuse War , which led to fighting from the Cascade Range to the Rocky Mountains . The Cayuse were defeated in 1855 , but the conflict had expanded and continued in what became known as the Yakima War ( 1855 – 1858 ) . Washington Territory Governor Isaac Stevens tried to compel Indian tribes to sign treaties ceding land and establishing reservations . The Yakama signed one of the treaties negotiated during the Walla Walla Council of 1855 , establishing the Yakama Indian Reservation , but Stevens ' attempts served mainly to intensify hostilities . Gold discoveries near Fort Colville resulted in many miners crossing Yakama lands via Naches Pass , and conflicts rapidly escalated into violence . It took several years for the Army to defeat the Yakama , during which time war spread to the Puget Sound region west of the Cascades . The Puget Sound War of 1855 – 1856 was triggered in part by the Yakima War and in part by the use of intimidation to compel tribes to sign land cession treaties . The Treaty of Medicine Creek of 1855 established an unrealistically small reservation on poor land for the Nisqually and Puyallup tribes . Violence broke out in the White River valley , along the route to Naches Pass and connecting Nisqually and Yakama lands . The Puget Sound War is often remembered in connection with the Battle of Seattle ( 1856 ) and the execution of Nisqually Chief Leschi , a central figure of the war
Whitman massacre
Whitman massacre
American Indian Wars