This Article is a revisionist history of the ratification of the Twenty-Fifth Amendment, which establishes procedures for remedying a vice presidential vacancy and for addressing presidential inability. During the Cold War, questions of presidential succession and the transfer of power in the case of inability were on the public’s mind and, in 1963, these questions became more urgent in the shadow of the Cuban Missile Crisis. Traditional legal histories of the Amendment argue that President John F. Kennedy’s assassination was both the proximate and prime factor in the development of the Amendment, but they do not account for the pervasive nuclear anxiety inherent in American politics and culture at the time. Oral interviews of key actors, such as former Senator Birch Bayh of Indiana, the Amendment’s architect, as well as examination of the Lyndon B. Johnson papers, the files of the Subcommittee on Constitutional Amendments, and other previously unexamined archives, offer new insight into the anxiety and thought processes of the President, Congress, and state legislators. With the ratification of the Twenty-Fifth Amendment on February 10, 1967, the nuclear anxiety of the era became ingrained in the Constitution itself. The framers of the Amendment adjusted America’s foundational document not as dictated by a momentary whim but by the exigencies of the times. With the goal of expanding the field of legal history by examining cultural and political factors, this Article argues that nuclear anxiety provides another important explanation for the incorporation of the Amendment.