Arco Map
Arco is a city in Butte County, Idaho, United States. The population was 995 at the 2010 census. The city is the county seat of Butte County.
Craters of the Moon National Monument is located along U.S. Route 20, southwest of the city. The Idaho National Laboratory (INL) is located east of Arco. Arco is located along the Big Lost River and is a gateway to the Lost River Valley.
In 1901, the town, then known as Root Hog, moved its borders to place the town at the intersection of two stagecoach routes that crossed Idaho. The town leaders applied to the U.S. Post Office for the town name of "Junction."
Nearby cities include Moore.