Battles & Wars › World War II › Manhattan Project
Oak Ridge (Clinton Engineer Works)
founded 1942; uranium enrichment 1943–45· Arms maker, factory or program· Arms makers & war industry
Well documentedSolid records, physical evidence or scientific consensus.
A secret city in Tennessee built from scratch to enrich uranium for the first atomic bomb.
See it on the Battles & Wars map →What happened
In 1942 the Army took about 59,000 acres of farmland along the Clinch River, displacing roughly 1,000 families on short notice. Architects Skidmore, Owings & Merrill planned a town that reached about 75,000 people by 1945. Giant plants separated rare uranium-235: Y-12's calutrons, whose magnets were wound with about 14,700 tons of silver borrowed from the Treasury, and K-25, then the world's largest building. Black workers lived in segregated plywood 'hutments.' Few workers knew what they were making.
Why it matters
It supplied the uranium for the Hiroshima bomb and became a lasting national laboratory for nuclear, materials and computing research.
Think of it like
A master-planned city built in under three years, its land assembled by condemnation, for a single secret tenant: the bomb.
How we know
Declassified Manhattan District records, Ed Westcott's official photographs, residents' oral histories, and the Manhattan Project National Historical Park, created in 2015.
Still debated
The health effects of mercury and radioactive releases on workers and nearby residents are still studied and argued in compensation cases.
Connections (3)
▸Oak Ridge (Clinton Engineer Works) enriched the uranium used at Hiroshima in the Atomic bombings of Hiroshima and NagasakiWell documented
The connection
Oak Ridge's plants took natural uranium, less than 1% uranium-235, and step by step concentrated it to bomb grade, using thermal diffusion, gaseous diffusion and Y-12's calutrons in sequence. The roughly 64 kilograms of uranium in the Hiroshima bomb came from there.
When and how
Oak Ridge, Tennessee, 1944 – July 1945; the Y-12, K-25 and S-50 plants, run by Tennessee Eastman, Union Carbide and other contractors.
How we know
Declassified Manhattan District production records and General Groves's postwar account.
Debates and open questions
How much each plant contributed is hard to pin down, since material moved among all three before final enrichment.
▸Oak Ridge (Clinton Engineer Works) shipped enriched uranium to Los Alamos LaboratoryWell documented
The connection
Enriched uranium from Oak Ridge was shipped to Los Alamos, where scientists measured it and machined it into bomb parts. By July 1945 there was enough highly enriched uranium for only one bomb, Little Boy, one reason the uranium design went untested.
When and how
Oak Ridge, Tennessee, to Los Alamos, New Mexico, 1944–1945, carried under guard by Army couriers.
How we know
Shipment and accountability records in declassified Manhattan District files.
Debates and open questions
How soon a second uranium bomb could have been ready is debated, and the exact delivery schedule is partly reconstructed from scattered records.
▸Oak Ridge (Clinton Engineer Works) relied on young women operators, part of Rosie the Riveter: women in war industryWell documented
The connection
At Y-12, thousands of young women, many just out of high school in rural Tennessee, ran the calutron control panels, adjusting dials without knowing their purpose. In a production contest, they reportedly outperformed the PhD scientists who designed the machines. These 'Calutron Girls' were part of the wartime wave of women in industry.
When and how
Y-12 plant, Oak Ridge, 1944–1945; operators employed by Tennessee Eastman, photographed by Ed Westcott.
How we know
Tennessee Eastman employment records, Ed Westcott's photographs, and operators' oral histories, such as Gladys Owens's.
Debates and open questions
The contest with the scientists is a famous story told by Manhattan Project participants, but its details rest on later recollection.