Arco is located at the point where the Lost River valley opens into the Snake River Plain. The Lost River flows past Arco on the west side of town, where it eventually disappears into a sink in the lava beds of the desert. The Lost River Mountains begin just east of Arco, and rise to the north, reaching a climax at Mount Borah, the highest peak in Idaho. The Lost River Valley reaches for some twenty-five miles northwest from Arco, a very flat and fertile farmland, bordered by majestic mountain peaks. To the south, the flat terrain of the Snake River Plain is broken by one mountain, named Big Southern Butte, which is the namesake of Butte County.
Arco was originally named “Root Hog,” but in 1901, the city limits were extended to include a nearby junction of stagecoach routes. The town applied to the U.S. Postal Service for the name of “Junction.” That name was considered to general, and the postmaster general suggested the name of Arco, after Georg von Arco, a German inventor who was visiting in Washington D.C at the time.
Arco is near the Idaho National Laboratory, where nuclear power was pioneered in the mid 1900s. Arco was the first city in the world to get electricity from nuclear power, on July 17, 1955. The Idaho National Laboratory (INL) is still a major employer for Arco today, and controls a large tract of land to the southeast.
Arco is still at a junction today, a junction of highways. There are three U.S. Routes that pass through Arco, but the alignments are shared in a complicated way. U.S. Highways 20 and 26 run east-west through the area. They approach from the southeast and turn at the main intersection in town to head southwest. U.S. Highway 93 is a north-south route which comes southward through the Lost River Valley into Arco, and also turns at the main intersection in town to go southwest. Thus all three routes are combined as they leave Arco to the southwest.
The railroad used to go through Arco, but has been removed now. The town is laid out parallel to the path it took, which was southeast to northwest, putting the town on a diagonal to the map. Front Street is the main street which fronted the railroad tracks.
Many tourists pass through Arco, headed to the Lost River Valley and Mountains, and to the nearby Craters of the Moon National Monument, along with other destinations. Both the lava fields of the Snake River Plain, and the mountains to the north are barriers to transportation, and alternative routes are few and far away.
On the mountains east of Arco, high school graduates have made a tradition of painting their years of graduation on the rocks for many generations. The large accumulation of numbers makes it a highly visible landmark, and it has become known as “Numbers Hill.”
The population of Arco was 995 at the 2010 census. The elevation ranges from about 5,310 to 5,400 feet in elevation. It is the county seat of Butte County.
For More Information:
See Wikipedia’s Arco, Idaho article.