Correction: An earlier version of this article misstated the area of Washington state.

Tennessee’s Oak Ridge National Laboratory was such a well-kept secret during World War II that most Americans still don’t know that it sits off one of busiest highways in the South.

Every year, streams of vacationers whiz by the complex that enriched uranium for America’s first atomic bomb project. It’s on the way to Great Smoky Mountains National Park — the most-visited U.S. national park. And every year, right about this time, the city of Oak Ridge, just west of Knoxville on Interstate 40, holds a Secret City Festival, crying out to potential tourists.

“They don’t even know we’re here,” said Katy Brown, president of the city’s convention and visitors bureau.

But a spotlight might shine soon on the Oak Ridge lab and two other largely forgotten Manhattan Project sites as the nation marks the 70th anniversary of the general order that established the world-shaking atomic research and development program.

The Obama administration is supporting bipartisan legislation in Congress that would designate sites in Oak Ridge; Hanford, Wash.; and Los Alamos, N.M., as national parks.

The designations would make possible wider exposure of the aging laboratories, which altered history — and, some say, darkened it.

The Hanford site produced plutonium. The Oak Ridge site enriched uranium. And workers in Los Alamos used those materials to assemble the Little Boy and Fat Man bombs dropped on Japan, forcing the Japanese surrender and ending the war. About 200,000 civilians in Hiroshima and Nagasaki perished.

The Advisory Council on Historic Preservation called the creation and use of the atomic bomb “the single most significant event of the 20th century’’ in advocating the preservation of buildings once scheduled for demolition.

The president of the Japanese American Association of New York is not as nostalgic. Any commemoration of the sites, Gary S. Moriwaki said, should educate visitors “on the devastating effects of the bombs dropped” on Japan.

“One should reflect on the words of J. Robert Oppenheimer: ‘I am become death, the destroyer of worlds,’ ” Moriwaki said. Oppenheimer, a physicist, guided the project at Los Alamos and has been called the father of the atomic bomb.

Today, thousands of scientists work in those labs on unrelated research, developing pioneering technologies used for Mars exploration, chemotherapy, whole-body X-ray scanning at airports, high-speed computers and biotechnology. This work is a legacy of the brilliant scientists who worked at the sites during World War II, Energy Department officials said.

“You can’t deny the impact nuclear weapons have had,” said Micah Zenko, a fellow at the Council on Foreign Relations who specializes in nuclear policy. Zenko said preserving the Manhattan Project sites makes sense. “It’s a part of American history that most people forget.”

Manhattan Project

America’s race with Nazi Germany to develop the first atomic bomb received its code name, the Manhattan Project, in late 1941. The establishment of the Manhattan Engineering District followed in August 1942.

Also in 1942, the Hanford reservation, along the Columbia River in eastern Washington, was selected to produce plutonium. The Oak Ridge and Los Alamos labs were established in 1943. In all, 125,000 people worked on the project at those sites and in Manhattan, but only about 1,000 knew the exact purpose of the work. About 32,000 people work at the two labs and Hanford now.

The labs and Hanford all have some nuclear-waste contamination, and they are undergoing cleanups involving up to 30,000 workers employed under multibillion-dollar contracts, said David G. Huizenga, senior adviser for environmental management at the Energy Department.

In Washington state, workers have nearly completed cleaning up a 220-square-mile area along the Columbia River, an Energy spokeswoman said. In Tennessee, workers are cleaning more than a third of the 52-square-mile site, focusing on parts of its three main campuses that worked with uranium. In New Mexico, workers are digging up 55-gallon drums, placing them in larger containers with better seals and burying them 21 feet underground.

Huizenga said he is certain that tourists can safely visit any Manhattan Project site. “Tours will steer well clear of contaminated areas. You would have to be directly digging up the waste to be at risk of being exposed by it,” he said.

Concerns about waste is one reason the government originally frowned on the idea of preserving buildings at Los Alamos and the other two sites. Among the notable structures are Oak Ridge’s mile-long K-25 building, one of the largest in the world during the war. Los Alamos still has the modest house that was once home to Oppenheimer. And there are historic sites that housed reactors and assembly plants, buildings that by the mid-1990s were falling apart.

“They were all to be destroyed,” said Cynthia C. Kelly, president of the Atomic Heritage Foundation, which worked to preserve them. “It was just kind of a quick and not very careful thinking of whether these were valuable properties.”

That thinking changed in 1997, when a team from the federal Advisory Council for Historic Preservation visited and team members were impressed by what they saw. Later the National Park Service recommended the establishment of parks at the sites that “could expand and enhance . . . public understanding of this nationally significant story in 20th century American history.’’

A park designation bill by Sen. Jeff Bingaman (D-N.M.) is slowly working its way through committee. Companion legislation by Rep. Doc Hastings (R-Wash.) is awaiting a vote by the full House, possibly next week.

‘It’s very nostalgic’

As a national park, Oak Ridge could easily top the roughly 1,500 visitors a year who tour the site now, said Brown, of the city visitors bureau. Tours are conducted by the Energy Department five days a week from June to September.

Brown has ridden the tour bus that boards at the nearby American Museum of Science and Energy and passes through the tall laboratory fence. The lab’s graphite reactor, she said, is an awesome sight.

“It’s really cool. It’s very nostalgic,” she said.

The tour included an old control room, where a logbook encased in glass recorded the time when the reactor first went critical, about 5 a.m. Nov. 4, 1943.

At the program’s peak, 75,000 people worked on the Manhattan Project at Oak Ridge. Sixty cents of every dollar for the project was spent there.

Brown said she wants more Americans to take the tour. She wants to grab some of the tourists who speed by on their way to Dollywood or the Smoky Mountains.

“We’re an ideal location to tell this story because people are driving past us all the time,” she said. “This would allow us to do more with what we have. Perhaps we could run it year-round.”

At Los Alamos National Laboratory,there are no tours currently, a spokeswoman said. Kelly, of the Atomic Heritage Foundation, said she hopes a park designation will open the site to tours that would include garagelike buildings where the bombs were assembled and Oppenheimer’s old house, a small cottage where a woman has lived since 1951.

The woman, 93, signed the house over to the Los Alamos Historical Society with the understanding that she could live there as long as she chose, Kelly said.

“When I first met her, she said, ‘You must come see the house,’ ” Kelly recalled. “She said, ‘I haven’t changed a thing.’ ”

Twitter: @darrylfears.