The Grande Ronde Massacre, also known as The Battle of the Grande Ronde, was a significant event that took place in northeast Oregon Territory on July 17, 1856, in what is now Union County. It involved an assault by 175 mounted volunteer soldiers on a Native American village inhabited by Walla Walla, Umatilla, and Cayuse families near present-day Elgin and Summerville, Oregon.[1][2][3] While the exact number of casualties among men, women, and children is unknown, the assault is recognized as the deadliest military-Native conflict in Oregon during the Indian Wars.[1][3] The attack resulted in the destruction of approximately 120 lodges and the loss of an estimated 150 horse loads of food and equipment, with over 200 horses captured.[1][3] The volunteer army suffered four deaths and four injuries during the incident.[1][3]