We stand at a barbed-wire fence, looking past a locked gate to a paved road that leads nowhere. Beyond a "Road Closed" sign and piles of dirt and rock, prairie grasses gone brown with the approach of winter drop eastward. In the distance, sheets of dust blow across the horizon. We have been told that behind the fence lies a stirring swath of High Plains ecology, a vast undeveloped acreage within one of the nation's fastest-growing suburban landscapes. We've been told that it's home to rare native xeric grasses and vital riparian habitat, to deer, elk, prairie dogs, pocket gophers, Preble's jumping mice, coyotes and badgers. And Wes McKinley, the Colorado state legislator who stands beside me peering through the gated entrance, has been told he cannot enter.

McKinley had followed protocol and asked the legislative staff at the state Capitol to request a tour of this land, now known as the Rocky Flats National Wildlife Refuge. One refuge manager agreed. The next morning, however, another called McKinley back to say there weren't enough funds to allow him on site. "I said I'll pay. They said they don't have enough personnel. I said I can go on my own. They said they'd arrest me," McKinley recalled. "I said, 'How? You don't have any personnel.' They said they had patrols. I asked if I could go with one of their patrols. They said it's closed to the public."

Not that McKinley actually wanted to visit the refuge. If allowed past the gate, he told me, "I was going to bring a mask." McKinley is a rancher from southeastern Colorado and he looks the part, with the white hat, blue neckerchief and scuffed cowboy boots, the handlebar mustache and the sandpaper handshake. He has set foot on the property only a handful of times, but his relationship with it has been protracted and contentious. The land was once home to the Rocky Flats nuclear weapons plant, and McKinley was foreman of a grand jury panel that, nearly 20 years ago, investigated allegations of unauthorized disposal and incineration of hazardous waste at the plant. Unhappy with the outcome of the investigation, he has, in the years since, clamored relentlessly for more disclosure of the environmental crimes that occurred here.

In 2004, McKinley won a seat in the state Legislature. He used that public perch to call attention to what he calls the "cover-up" at Rocky Flats -- co-writing a book, The Ambushed Grand Jury, and expounding on the subject to any journalist willing to listen. That same year, he also participated in an oral history project sponsored by the planned Rocky Flats Cold War Museum to collect the stories of Rocky Flats employees, community leaders, activists, regulators, politicians and others who had been involved with the plant. Historian Dorothy Ciarlo and I conducted more than 90 video interviews for the future museum, whose board incorporated in 2001. The oral histories were essential to its mission of documenting the historical legacy of Rocky Flats, because what was made there remains a tightly held secret. To this day, it is illegal to mention the weight, circumference, mass or specific composition of the products that were made at Rocky Flats. In addition, the vast majority of the site's "artifacts" were so saturated with 40 years of radiological pollutants that it required thousands of workers to painstakingly dismantle and ship them to highly secured nuclear-waste disposal sites.

Between 1952 and 1989, Rocky Flats produced as many as 70,000 plutonium "pits" -- the small, fissile atomic detonators at the core of every bomb in the nation's nuclear arsenal -- on an immense industrial complex 15 miles northwest of Denver. It grew to become a veritable city, employing thousands of machinists, metallurgists, janitors, physicists, chemists, biologists, radiation specialists, engineers, secretaries, security guards, firemen, accountants and administrators. The plant's neighbors initially welcomed the jobs Rocky Flats brought. After a near-catastrophic fire in 1969 gutted two plutonium buildings, however, local leaders, concerned neighbors and anti-nuclear activists began to question the wisdom of having a nuclear weapons plant so close to a rapidly developing urban area. In 1989, after decades of mounting protest, the FBI and the Environmental Protection Agency raided the site and found multiple violations of federal anti-pollution laws. Production was halted, and in 1992, the first President Bush announced that the plant would close for good.

Over the next decade and a half, the U.S. Department of Energy oversaw the decontamination and demolition of the plant's 800-plus buildings and structures. This was no easy task: At the time production ended, the site housed 13 metric tons of plutonium, some in liquid form and stored in deteriorating piping systems, underground waste lines and leaking storage containers, and a smorgasbord of some of the most hazardous substances on earth -- uranium, americium, beryllium, dioxin, along with carbon tetrachloride and a number of other acids used to dissolve plutonium. The $7 billion cleanup represented the largest and most complex nuclear site remediation in history. In December 2006, the DOE certified the cleanup as officially "complete" and divided the 6,500-acre site into two parcels: 1,300 acres in the contaminated industrial center were to be retained by the DOE for long-term surveillance and maintenance, off-limits to visitors; the outer 4,000 acres, meanwhile, would become America's newest federal wildlife refuge.

McKinley thinks that was a terrible idea. He maintains -- as do a number of former activists, regulators and retired employees -- that Rocky Flats poses a hazard to anyone who sets foot on the site or lives nearby. He believes that beneath the refuge lies a buried history that the public has every right to know but little recourse to uncover. As Rocky Flats and other nuclear facilities across the West recede into the past, he wants to make sure we don't forget.