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.