The discovery of gold on the upper Columbia River drainage in the summer of 1855 brought a large influx of miners into the area, trespassing on the land that was promised (during the Walla Walla Council (1855)) to many of the tribes in the area, including the Yakima. This violation angered the tribes who felt that the promises that had been made to them by the United States government were not being honored. This led to a retaliation through the murder of the Indian agent for that area, thereby inciting the Yakima War. The local tribes were defeated, and Stevens held a peace council at Fort Walla Walla in September 1856 that brought an end to the Yakima War.