The Bear River Massacre, or the Engagement on the Bear River, or the Battle of Bear River, or Massacre at Boa Ogoi, took place in present-day Franklin County, Idaho, on January 29, 1863. After years of skirmishes and food raids on farms and ranches, the United States Army attacked a Shoshone encampment gathered at the confluence of the Bear River and Battle Creek in what was then southeastern Washington Territory, near the present-day city of Preston. Colonel Patrick Edward Connor led a detachment of California Volunteers as part of the Bear River Expedition against Shoshone tribal chief Bear Hunter. Hundreds of Shoshone men, women, and children were killed near their lodges; the number of Shoshone victims reported by local settlers was higher than that reported by soldiers.

Franklin County is a county located in the U.S. state of Idaho. As of the 2020 Census the county had a population of 14,194. The county seat and largest city is Preston. The county was established in 1913 and named after Franklin D. Richards, an Apostle of the Church of Jesus Christ of Latter-day Saints. It is the only Franklin County in the United States that is not named after Benjamin Franklin. Franklin County is part of the Logan, UT-ID Metropolitan Statistical Area.