Experimental Breeder Reactor Number One (EBR-I) has the distinction of being the world's first experimental nuclear power plant. EBR-I is a Registered National Historic Landmark in the desert about 18 miles southeast of Arco, Idaho. On December 20, 1951, a successful experiment at EBR-I proved the viability of nuclear power by illuminating four light bulbs. Thus the facility truly is the world's birthplace of usable atomic energy from a nuclear reactor.

Part of the National Reactor Testing Station (now known as INEEL), EBR-I's construction started in late 1949. The reactor itself was designed by a team led by Walter Zinn at the Argonne National Laboratory. Installation of the reactor at EBR-I took place in early 1951 and the first reaction went critical on August 24 1951. On December 20 of that year, atomic energy was successfully harvested for the first time. Interestingly, the design purpose of EBR-I was not to produce electricity but instead to validate nuclear physics which suggested that a breeder reactor should be possible. In 1953, experiments revealed the reactor was producing additional fuel during fission, thus confirming the hypothesis. However, on November 29, 1955, the reactor at EBR-I suffered a partial meltdown due to operator error. It was subsequently repaired for further experiments.

Besides generating the world's first electricity from atomic energy, EBR-I was also the world's first breeder reactor and the first to use plutonium fuel. EBR-I was deactivated in 1964 and replaced with a new reactor, EBR-II. Landmark status for EBR-I was granted by President Lyndon Johnson and Glenn T. Seaborg on August 25, 1966. The site has been open to the public since 1976, however it is only open between the Memorial Day and Labor Day holidays. Also on display at the site are two prototype reactors from the Aircraft Nuclear Propulsion Project of the 1950s.