Alturas County was a county in Idaho Territory and later the state of Idaho from 1864 to 1895. It covered an area larger than the states of Maryland, New Jersey, and Delaware combined. Most present-day southern Idaho counties were created at least in part from the original Alturas County area. The name Alturas comes from a Spanish word for "mountain summits" or "mountainous heights." Alturas County was created by the Idaho Territorial Legislature in February 1864. Later that year the mining camp of Rocky Bar was designated the county seat. The county seat was moved to Hailey in 1882.