Oak Ridge was an entirely government-run town that was closed to the general public, where tens of thousands of people lived at any given time. It was in this sense highly unusual — it was more socialistic than any other community in the United States at the time. The government (specifically, the military through contractors and subcontractors) worked to control nearly every aspect of economic and social life there, down to the details of what kind of products were sold in what kinds of establishments, to the kinds of sports that were on offer for people to do. All in an atmosphere that emphasized total secrecy and the fact that nearly nobody there actually knew what it was they were developing. Everyone, from the employees to the people who ran it, considered it to be a highly unusual place as a result.

Most of the workers there did have no knowledge of the ultimate aims of what they were doing. As far as they knew they were doing construction, or just turning a knob. A Calutron operator, for example, would know that their job was to watch a meter. If the needle went too far one way, they turned the knob the other way. Repeat all day long. What's the knob and needle controlling? That's a secret. What's the ultimate point of the factory? That's a secret.

(In reality, they were adjusting the paths of uranium ions as they looped through a magnet field, which allowed a collector to skim off a portion of it that contained more of one isotope of uranium than the bulk of it. Most of the operators would have had no idea what that sentence meant and in fact most Americans still would have trouble parsing that as I have written it — this is still pretty high-tech stuff. To then go from that operation to the idea that this would be used for a nuclear fission weapon that could destroy a city was a further big leap.)

Obviously people speculated about what it was they were actually doing, and rumors circulated. Some understood it was some kind of weapon. Some thought it was just some kind of boondoggle. Some probably figured out it had something to do with atomic energy. The secrecy was never perfect. But manufacturing enough uncertainty meant that little came of such rumors and speculation, and there was an accurate sense that anything that went too far would attract the attention of the security forces and lead to a termination of the job if not worse.

It was a highly unusual atmosphere, different in many ways from the other major Manhattan Project sites (Hanford and Los Alamos) in its size (60% of the project people and money went into Oak Ridge) and its self-containedness (Hanford was not nearly so holistically run; Los Alamos was but more people had a sense of what they were doing there). It should not be assumed that people enjoyed this part of the work: they had terrible turnover rates at Oak Ridge, month to month, which could be as high as 15 or 20%. That's a lot of people to replace every month, especially as the total number of people working there grew. The secrecy was credited for part of that turnover: people don't like to not know what they are working on, or work on something that, as far as they can tell, has not contributed one bit to the overall war effort.

I've written a bit more about Oak Ridge life and the secrecy here. It includes some interesting anecdotes from a postwar radio series, where people who worked there described what it was like to work on things you did not understand, often in a repetitive way.

On the turnover rate, see here. For a history of social life at Oak Ridge, see esp. Denise Kieran's The Girls of Atomic City, and Lindsey Freeman's Longing for the Bomb.