Manhattan Project: personnel by sector 1944

Throughout the existence of the Manhattan Project, from 1941 until 1946, over half a million people were employed in the project in some capacity. In June 1944, as the time of the Allied invasion of Normandy, there were almost 130,000 people employed in the Manhattan Project, however, the vast majority of those were employed in a construction capacity, while fewer worked in administrative, custodial, or service-based capacity. Only a small share of the project's workforce was actively involved in the research and development of nuclear weapons, while a smaller number still were militarily involved in the project (in areas such as espionage, reconnaissance, or strategic bombing). For the majority of workers in the Oak Ridge or Hanford sites; the largest two sites involved in the project; they did not learn of their contribution to the production of nuclear weapons until after the attacks on Hiroshima and Nagasaki.