Clinton Engineer Works The Clinton Engineer Works ( CEW ) was the Army name for the Manhattan Project production facility in World War II for enriched uranium ( Uranium 235 ) used in the Little Boy atomic bomb dropped on Hiroshima in 1945 , and would have produced enough enriched uranium for a second Little Boy gun - type bomb by December 1945 . The secret “ semiworks ” plant is on Oak Ridge in the eastern part of the U . S . state of Tennessee , about west of Knoxville , and was named after the town of Clinton , Tennessee , to the north . The plants are mainly in Roane County with the northern part of the site in Anderson County . The construction workers for the K - 25 and other plants were housed in a community known as Happy Valley . Built by the Army in 1943 , the temporary Happy Valley community housed 15 , 000 people in trailer homes . The town of Oak Ridge was established to house the production staff . The operating force peaked at 50 , 000 workers just after the end of the war . The construction labour force peak was 75 , 000 and the combined employment peak was 80 , 000 . Developed by the federal government as a segregated community , black residents lived only in an area known as Gamble Valley , in government - built " hutment s " ( one - room shacks ) on the south side of what is now Tuskegee Drive . Ken Nichols the MED Deputy District Engineer from June 1942 and District Engineer from August 1943 was responsible for the Clinton and Hanford production “ semiworks ” , and their houses were of a higher quality than those approved by Groves at Los Alamos . He moved the Manhattan District headquarters from Manhattan , New York to CEW in August 1943 . In 1954 Nichols transferred responsibility for coordinating supply of feed materials for both Oak Ridge and Hanford to Oak Ridge from New York , as with only two plants " the need for coordination had essentially been eliminated ( but ) as usual in government operations , no one wanted to take the onus of telling employees they no longer are needed . " Establishment . A survey team from the engineering company Stone & Webster had already scouted a site for the production plants , and recommended several sites in the Knoxville , Tennessee area , an isolated area where the Tennessee Valley Authority could supply ample electric power and the rivers could provide cooling water for the reactors . Site X or the Oak Ridge site , selected by James Marshall and Nichols in June 1942 had : Marshall had delayed purchase of the site until at least the chain reaction was proven , but on taking over Groves immediately ( 19 September ) approved purchase of the 52 , 000 acres of land required . On 23 September the newly promoted Groves impressed Secretary of War Stimson and others at his first meeting with them by leaving early to catch the train to Tennessee to " inspect Site X . " Postwar , on 19 March 1949 , the residential and commercial portion of Oak Ridge , known as the " townsite , " was opened to public access , and access to the AEC facilities was controlled by three gatehouses which replaced the seven wartime gates : Blair Gate to Harriman , Oliver Springs Gate , Elza Gate to Clinton , Edgemoor Gate to Clinton , Solway Gate to Knoxville , White Wing Gate to Lenoir City and Gallaher Gate to Kingston . Facilities . Three of the four major wartime facilities are still standing today : Operation . The three uranium enrichment plants had different capabilities : Nichols realised in autumn 1944 that coordinating the use of the three plants would be much more difficult than anticipated . Initially it was planned to feed 1 . 1 % material from K - 25 into the Y - 12 alpha stages , and as sufficient sections of K - 25 were completed use them to produce 20 % or higher enriched material to feed into the Y - 12 beta stages . But a considerable equilibrium time was necessary to move from 1 . 1 to 20 % . In early September he appointed a production control committee , headed by A . V . ( Pete ) Peterson ( a reserve officer , and his wife ’ s sister ’ s husband ) . Peterson ’ s staff tried various combinations , using mechanical calculating machines , and decided that the S - 50 production should be fed to K - 25 rather than Y - 12 , which was done in April 1945 . The charts also showed that the proposed top stages for K - 25 should be abandoned , as should Lawrence ’ s recommendation to add more alpha stages to the Y - 12 plant . Groves accepted their proposal to add more base units to the gaseous - diffusion plant ( K - 27 not K - 25 ) and one more beta stage track for Y - 12 . These additions were estimated to cost $ 100 million , with completion in February 1946 . Because the enriched uranium was shipped out discretely by courier in a suitcase , there was a local rumour that the secret CEW project must be a failure or a boondoggle . Many of the local residents and workers observed that thousands of railroad cars were carrying supplies into the CEW but no one had ever seen anything shipped out .