Leroy Jackson was transferred into the Manhattan District, the branch of the United States Army Corps of Engineers tasked with overseeing the construction of critical Manhattan Project sites, shortly after its formation in 1942. He lived and worked at Oak Ridge during the war and was closely involved in the design and construction of the site’s thousands of residential units and cafeterias and recreational facilities, as well as the Y-12 and K-25 Plants and the X-10 Graphite Reactor.