This essay explores the evolution of American nuclear targeting during World War II. Initial discussions in Washington focused on the use of the bomb against a military target. The assumption that cities would be the primary target for the atomic bomb apparently originated at Los Alamos in 1943 - 44, largely as a result of technical concerns related to the delivery and functioning of the weapon. Some high-level officials in Washington voiced reservations about the use of nuclear weapons against primarily civilian targets. Ultimately, the accumulated momentum of previous technical decisions and a desire to use the bomb as quickly as possible for military-diplomatic reasons convinced the President and his advisors to overcome reservations about targeting Japanese cities and civilians.