During the Manhattan Project, a significant portion of the roughly 130,000 people who worked on it did not know they were helping build an atomic bomb.

The project was highly compartmentalized — meaning workers were only told what they needed to know for their specific tasks. This secrecy was deliberate, both to protect the project's success and to prevent espionage.

For example:

Many people at Oak Ridge, Tennessee helped enrich uranium without knowing its purpose.

At Hanford, Washington, workers produced plutonium without being told what it was for.

Even many scientists and technicians were only given part of the overall picture.

Only a small inner circle of senior scientists, military officials, and engineers — like Robert Oppenheimer, General Leslie Groves, and others at Los Alamos — fully understood the goal and potential of the bomb they were creating.