Nuclear reactions were first mastered in Illinois, but arguably Idaho gets credit for the first generation of electricity via nuclear reactor with the 100kW EBR-1 in 1951. Credit for the first grid-tied nuclear power plant goes to the Soviets, with the commissioning of the the Obninsk Nuclear Power Plant in 1954. Curiously the latter produced a miniscule amount of power by modern standards, with a mere 5MW of nameplate capacity.