Atomic City is a city in Bingham County, Idaho, United States. The population was 41 at the 2020 census, up from 29 in 2010. Atomic City was called "Midway" until 1950, as it is halfway between the towns of Blackfoot and Arco. Atomic City had a larger population when the neighboring Idaho National Laboratory site was newer, known as the "National Reactor Testing Station" until 1975.