As white settlers poured into the Oregon Country in the 1830s and 1840s, the Cayuse and Umatilla tribes were increasingly threatened. What began as small scale missionary work came to be seen by Native groups as increasingly threatening and coercive. Violent incidents between the groups increased. Lethal outbreaks of disease spread among the Natives.
In response to these incursions, on November 29, 1847, the Cayuse attacked a party of seventy-two settlers, killing thirteen, including their leader, Marcus Whitman, and holding the rest captive for weeks in exchange for goods.
As white settlers gained power and claimed sovereignty over the territory, which was organized and recognized by Congress as the Oregon Territory in 1848, their demands that the Cayuse be held legally responsible for the Whitman Massacre intensified. Cayuse efforts to characterize the incident as an act of war and to note their own losses were rejected.
Eventually, five Cayuse men – Tiloukaikt, Tomahas, Kiamasumpkin, Iaiachalakis, and Klokomas – were turned over for trial. The legal proceedings were conducted in a tavern with minimal due process protections.
U.S. Attorney Amory Holbrook tried the men before federal judge Orville C. Pratt in Oregon City, Oregon. After a lengthy and controversial trial, in which the defense emphasized the lack of federal jurisdiction over the case at the time of the killings, all five men were found guilty and sentenced to death.
Their hanging, on June 3, 1850, on a gallows constructed in Oregon City, was organized by U.S. Marshal Joseph L. Meek, whose daughter died while being held captive by the Cayuse.
Five years later, the Cayuse were forced on to the Umatilla Reservation.