I interviewed dozens of former plant employees for the oral history project, and they invariably described Rocky Flats as a well-run, well-oiled machine that helped to safeguard American liberty. Those interviews were often most memorable for their very sameness. When asked about safety at Rocky Flats, former employees often began with a little joke: "I don't glow in the dark," they'd say. Then they would continue: "I've never worked in a safer place." They had a point: Rocky Flats had an impressive short-term industrial safety record and regularly went months without injuries to its workers. "We ran the plant for 40 years, and I think there were three deaths," recalled Ed Vejvoda, who joined Rocky Flats in 1952 and was chief of plutonium operations from 1976 to 1987. "Two were due to vehicles. … There were no deaths in the production part at all."

But Jerry San Pietro worked at the same plant for almost 30 years, and, although he too believed his career at Rocky Flats helped keep this country free, he begged to differ. When I interviewed him in 2005, he had been retired for a decade and was in his late 50s, with weathered skin, a shock of thick salt-and-pepper hair and an equally imposing mustache. He favored flannel shirts and work boots, and walked with a painful limp acquired after his hunting buddies dropped an elk on him five years earlier. San Pietro started as a janitor at Rocky Flats in 1966, just out of high school, after learning of a job opening from an uncle who worked there. For some time after he started, he had no idea what the plant did. "I knew it was something to do with radioactive material, but I didn't know what," he said. "One day my crew leader said, 'You know what they do back there?' I said, 'No.' And he took me behind the double door of the airlock, and I just went, 'Oh!' There was dryboxes and gloves and stuff I couldn't imagine."

After a few months as a janitor, he began taking night courses in chemistry and applied for a lab-tech position. Then, when the massive 1969 fire rampaged through two adjoined plutonium processing buildings, San Pietro enlisted as a radiation monitor, donning an Army assault mask with an oxygen canister and two eyeholes and trailing cleanup workers as they mucked through the radioactive stew of chemicals, plastics, acids and plutonium in the burned buildings. "They gave me an instrument and said, 'If it clicks, it's hot, and if it doesn't, it's cold. Go in there and tell people when it's hot and cold.' "

The radiation monitors were the eyes of the site, in charge of preventing and measuring contamination in the "hot" areas where the radioactive materials were processed. It was nerve-racking work. As the chemical operators handled highly reactive plutonium solutions and metals, monitors like San Pietro hovered beside them with clicking Geiger-counter-like devices. They monitored jobs throughout the warehouse-like buildings, listening for the crackling of their belt-hung monitors and the screaming of room alarms, and watching for less obvious signs of escaping radiation, like unmanned gloves thrusting outwards from the multi-story metal-and-leaded-glass "glove boxes," indicating that contaminated air was blowing into the room. "You'd find a barrel that (was) kind of wobbly, and you'd think, 'It's bending the bottom out,' " San Pietro remembered. "Or you'd be walking along and you'd find a whole bunch of green liquid on the floor, which was plutonium nitrate … and there was gallons of it running everywhere."

Once, walking through the building, he felt a drip on his head. "I took my probe and put it on my hair, and it went, 'Kchhhh!' -- infinity. Then I felt another drop hit on my shoulder. And I looked up, and there was a plutonium nitrate line leaking right above me." When something like that happened, he went straight to medical, where his hair would be shaved and his skin scrubbed with Clorox to remove the contamination. But San Pietro could report none of this to his family. "I could never tell them when something blew up or caught fire," he said. "I'd go home with bandages on me and they'd say, 'What happened?' I'd say, 'Well, I just got hurt.'"

Every employee at the plant would have been expected to provide a similarly vague response. It was the Cold War, after all. Rocky Flats was ringed by concertina wire, deserted ranchland and guards armed with submachine guns, and its very existence was, for many years, a secret. Potential employees underwent rigorous FBI background checks, and many received the highest "Q-clearance" security authorization. Like San Pietro, many were unaware of what the plant did until well after they arrived. They were not allowed to discuss their jobs with friends or family; workers recalled telling outsiders they made everything from Saran Wrap to glass doorknobs. Nor could employees share information with each other. "I would go on a special project, cleared for that project, and (my boss) wasn't," said Vejvoda. "I would come back and he would say, 'What did you do?' I said, 'I can't tell you.' "

This "compartmentalization," as it is known in intelligence circles, is a cornerstone of national security policy, limiting access to information to those who have a direct "need to know." Such secrecy is essential in the world of nuclear weapons; it is problematic, however, for those seeking to understand Cold War history, because it means that everybody, by design, saw only their small piece of the much larger story. This has made the task of memorializing such a furtive complex of buildings a challenging one: Rocky Flats' secrecy not only fragmented the plant's knowledge of its own processes, it also splintered its history. Radiation monitors like San Pietro, for instance, described a very different workplace from metalworkers who machined beryllium or the physicists in the lab or managers in the administrative offices.

Oral history is an attempt to record memories from an individual perspective, not an objective means of explaining exactly "what happened." When oral histories proliferate, however, those personal, subjective stories can combine to achieve a critical mass, creating a historical fusion of sorts that allows us to see the larger picture. And some of the people we interviewed did have a larger view. Nat Miullo, for instance, was an EPA inspector in charge of oversight of Rocky Flats in the 1980s. At times, he was escorted to inspection sites blindfolded to protect the secrecy of operations he wasn't cleared to witness. Over the years, however, "I found myself … in a position of knowing more about the operations of the plant than the actual people who worked there," Miullo said. So did Wes McKinley, who, as a grand juror, was privy to documents collected by the EPA and FBI after the 1989 raid and never released to the public.

And so did Jerry San Pietro. Over the years, San Pietro acquired a reputation for refusing to "buckle under to supervision." Despite intense pressure from his managers to keep production rolling, he did not hesitate to stop work on jobs he considered unsafe. Eventually, the union asked him to chair the Joint Company-Union Safety Committee, which monitored working conditions for hourly employees. It was in that capacity that he conducted his own oral history of sorts. And many years later, when the Energy Department proposed the creation of the Rocky Flats Wildlife Refuge, he found himself compelled to share what he had learned.