This article traces the history of the development and construction of the first prototypes and operating nuclear power plants, all as part of the Manhattan Project. Beginning with CP-1, the first self-sustained nuclear chain reaction in 1942, it details subsequent Manhattan Project reactors and then examines the construction and operation of the first modern nuclear power plants built at Hanford, Washington. These were built for the sole purpose of manufacturing plutonium for nuclear weapons. The article argues that nuclear power was born violent: it was invented as part of the manufacturing process of nuclear weaponry. This argument goes beyond previous historiography focusing on the technological development of nuclear power to emphasize the purpose of its development, the mass and indiscriminate killing of human beings.