A history of the United States’ experience with radiological weapons, from inception during the Second World War through the Cold War. A taxonomy of Radiological Warfare (RW) is presented, defining RW as a fringe of other forms of warfare. The history details an evolution from RW as a form of chemical warfare into an aspect of nuclear warfare. As a type of chemical weapon for area denial, there were successful field experiments, and logistical challenges to adoption. As a tactic of nuclear warfare, the base surge could be exploited for RW area denial. The RW effect was a bonus with the cratering for atomic barriers. The use of fallout for RW was more problematic, distinguishing between reliable RW effect and undesirable consequences. Salting and dirty strategic nuclear weapons were explore, with the later being adopted for war planning which ignored the contribution of fallout. The complexities of adopting tactical nuclear weapons resulted in a de facto RW doctrine, which led to emphasis of initial radiation in upgrading weapon systems, viz., Enhanced Radiation (ER) weapons. Public opposition to the neutron bomb prevented the deployment of ER weapons, and the end of the Cold War disestablished the America’s RW doctrine.