The Cayuse War, an armed conflict that takes place in the Northwestern United States from 1848 to 1855 between the Cayuse people of the region and the United States Government and local Euro-American settlers, had been caused in part by the influx of disease and settlers to the region.

The immediate start of the conflict occurs in 1847 when the Whitman Massacre takes place at the Whitman Mission near present day Walla Walla, Washington when fourteen people are killed in and around the mission.

Over the next few years the Provisional Government of Oregon and later the United States Army battles the Native American peoples east of the Cascades.

This is the first of several wars between the original inhabitants and Euro-American settlers in that region that will lead to the placement of many of the Native Americans onto Indian reservations.