Nuclear power in the United States has had an uneven history and faces an uncertain future. Promising in the 1950s electricity “too cheap to meter,” nuclear power has failed to come close to that goal, although it has carved out approximately a 20 percent share of American electrical output. Two decades after World War II, General Electric and Westinghouse offered electric utilities completed “turnkey” plants at a fixed cost, hoping these “loss leaders” would create a demand for further projects. During the 1970s the industry boomed, but it also brought forth a large-scale protest movement. Since then, partly because of that movement and because of the drama of the 1979 Three Mile Island accident, nuclear power has plateaued, with only one reactor completed since 1995. Several factors account for the failed promise of nuclear energy. Civilian power has never fully shaken its military ancestry or its connotations of weaponry and warfare. American reactor designs borrowed from nuclear submarines. Concerns about weapons proliferation stymied industry hopes for breeder reactors that would produce plutonium as a byproduct. Federal regulatory agencies dealing with civilian nuclear energy also have military roles. Those connections have provided some advantages to the industry, but they have also generated fears. Not surprisingly, the “anti-nukes” movement of the 1970s and 1980s was closely bound to movements for peace and disarmament. The industry’s disappointments must also be understood in a wider energy context. Nuclear grew rapidly in the late 1960s and 1970s as domestic petroleum output shrank and environmental objections to coal came to the fore. At the same time, however, slowing economic growth and an emphasis on energy efficiency reduced demand for new power output. In the 21st century, new reactor designs and the perils of fossil-fuel-caused global warming have once again raised hopes for nuclear, but natural gas and renewables now compete favorably against new nuclear projects. Economic factors have been the main reason that nuclear has stalled in the last forty years. Highly capital intensive, nuclear projects have all too often taken too long to build and cost far more than initially forecast. The lack of standard plant designs, the need for expensive safety and security measures, and the inherent complexity of nuclear technology have all contributed to nuclear power’s inability to make its case on cost persuasively. Nevertheless, nuclear power may survive and even thrive if the nation commits to curtailing fossil fuel use or if, as the Trump administration proposes, it opts for subsidies to keep reactors operating.