Established February 4, 1864 by the First Idaho Territorial Legislature with its county seat at Florence. In 1861 it had been established as the third county of the Washington Territory. Named for the Steamer Idaho that was launched June 9, 1860 on the Columbia River and served miners during the gold rush in north Idaho. In 1875 Mount Idaho was named the county seat, in 1902 the county seat was moved to Grangeville following a 10-year struggle between Grangeville and Mount Idaho.
County Seat: Grangeville