Arco, ID

Arco is the Butte County seat and largest city, set in the Lost River Valley at the junction of U.S. 20 and U.S. 26. The 2020 census counted 879 residents. Butte County's administration building, Arco Elementary, and Butte Middle-High School all sit in town, giving the small city a countywide civic and school role. The city is about 23 miles west of Idaho National Laboratory and 18 miles north of Craters of the Moon National Monument, so research work, farming, and desert recreation all sit in the surrounding map.

ATTRUser:akampfer / CC BY-SA 3.0

Arco became the first city powered entirely by nuclear fission in 1955, a milestone still carried in Butte County's identity. The city name appeared by 1860 and is linked to rancher Louis Arco. Number Hill rises above the school campus, where graduating classes paint their year on the slope. Highways lead west toward Mountain Home and east toward Idaho Falls, while U.S. 26 runs toward Shoshone and Blackfoot. County offices, school buildings, the highway junction, and the Lost River give Arco its present-day shape.