The Idaho Town That Ran on Nuclear Power for Two Hours

What happened on July 17, 1955?

The reactor responsible was BORAX-III, short for Boiling Water Reactor Experiment No. 3.

Scientists at Argonne National Laboratory were studying whether a boiling-water nuclear reactor could produce electricity reliably enough for practical use.

For the demonstration, BORAX-III was connected to a turbine-generator system. Argonne's historical account describes approximately 2,000 kilowatts of electricity generated during the test.

Of that output, approximately 500 kilowatts served Arco. Another 1,000 kilowatts supplied the testing station's Central Facilities Area, and roughly 500 kilowatts supported the BORAX installation itself.

The experiment lasted about two hours, according to Argonne's reactor history.

For that period, Arco became the first town in the world to receive its entire electricity supply from nuclear energy.

Why Idaho was testing nuclear reactors

The demonstration was not an isolated stunt. It was part of a much larger scientific effort underway in the eastern Idaho desert.

The federal government established the National Reactor Testing Station in 1949 as a location for developing and testing nuclear reactor technology.

The site's relatively remote setting offered space for experimental facilities and the engineering work associated with an emerging technology.

The BORAX program investigated boiling-water reactors, in which heat from nuclear fission boils water to produce steam for electricity generation.

These experiments contributed to knowledge that would inform later commercial nuclear power systems.

Arco's achievement was different from the four-lightbulb milestone

Idaho had already made nuclear history nearly four years earlier.

On December 20, 1951, Experimental Breeder Reactor-I, or EBR-I, generated enough usable nuclear electricity to illuminate four lightbulbs. That achievement helped establish that a nuclear reactor could produce practical electrical power.

The 1955 Arco demonstration answered a different question.

Could a reactor deliver electricity beyond its own experimental facility and supply a real community?

BORAX-III demonstrated that it could, at least for a limited period.

The distinction matters: EBR-I's 1951 milestone was the first production of usable nuclear electricity, while BORAX-III's 1955 milestone was the first complete nuclear electricity supply to a town.

Did Arco stay nuclear-powered?

No. The two-hour event was a demonstration, not the beginning of permanent nuclear service to the town.

Arco's achievement is sometimes shortened into the claim that it was the world's first nuclear-powered city. That description is historically meaningful, but it can create the impression that the community operated continuously on nuclear power afterward.

The more precise statement is that Arco became the first community supplied entirely by nuclear-generated electricity during a controlled demonstration.

BORAX-III remained an experimental reactor and operated until 1956.

What happened to the reactor?

The BORAX program continued developing and evaluating boiling-water reactor technology.

BORAX-III was followed by other experimental designs, including BORAX-IV and BORAX-V. Each explored additional engineering questions related to reactor operation, fuel and steam generation.

The work helped establish technical knowledge that extended far beyond Arco.

The reactor testing station itself evolved through several organizational changes into the research complex now known as Idaho National Laboratory.

Idaho's nuclear history therefore includes more than one famous experiment. It reflects decades of research, successes, failures and engineering lessons.

Can you visit Idaho's nuclear history today?

The BORAX-III demonstration site is not presented as a routine public attraction.

However, the nearby Experimental Breeder Reactor-I Atomic Museum preserves another major chapter of the same history. Visitors can learn about the reactor that produced usable nuclear electricity in 1951 and see the facility associated with that achievement.

The U.S. Department of Energy has historically offered seasonal museum access from Memorial Day weekend through Labor Day weekend. November visitors should not assume the museum is open.

Check current arrangements through Idaho National Laboratory before planning a visit.

For a longer drive through eastern Idaho, consult the Idaho road conditions guide and current highway information before departing.

A small town with a large place in energy history

Arco's two-hour demonstration did not immediately transform how every American household received electricity.

It did establish a memorable milestone: nuclear energy could supply an entire community, not merely power equipment inside a research building.

The accomplishment belonged to a wider effort involving scientists, engineers, federal research institutions and the communities surrounding the testing station.

More than seven decades later, the distinction remains worth understanding.

Arco was not permanently powered by a nuclear reactor in 1955. For two hours, however, it showed what was technically possible.