This sign marks historical reactors at the Idaho National Laboratory (INL), located in the high desert of eastern Idaho, approximately 18 miles southeast of Arco.
The site, formerly known as the National Reactor Testing Station, was the location for major milestones in nuclear history:
- EBR-I (Experimental Breeder Reactor No. 1): In 1951, it became the first power plant to generate usable electricity from atomic fission, famously lighting four 200-watt bulbs. It also proved that a reactor could "breed" more fuel than it consumed.
- BORAX (Boiling Water Reactor Experiment): Specifically BORAX-III, which in 1955 made nearby Arco, Idaho, the first city in the world to be powered entirely by nuclear energy.
- ZPR-III & AFSR: These were experimental reactors used for research into fast reactor physics and neutron sources.