Although it was established in 1942, the city of Oak Ridge, Tennessee, did not appear on a map until 1949. During that time, its 75,000 residents had their telephones tapped, their mail censored, their use of cameras restricted, and their cars routinely searched by armed guards at city gates. Access to the city was limited to residents, workers and approved visitors, frustrating salesmen and unwelcome relatives. Each worker performed his or her individual task, unaware of its ultimate purpose, and all were forbidden from talking about their jobs.

Why such security? Oak Ridge, then known as Clinton Engineer Works after the nearby town of Clinton, was part of the Manhattan Project, code name for the United States atomic weapons program. Only when the bomb was dropped on Hiroshima did most Oak Ridgers learn what their role in World War II had been.

Located in the Appalachian foothills 20 miles west of Knoxville, Oak Ridge was chosen because it met military requirements for isolation, water, electric power and accessibility to highways and railroads. In addition, few families would have to be displaced to build production facilities there.

Some of the same characteristics, such as its accessibility to transportation and water, make Oak Ridge a pleasant place to visit today. And this once "secret city" has adapted its atomic heritage to fit the needs of a more peaceful world.

Designed as a planned community, the city featured single-family homes based on set floor plans and designated by letters of the alphabet according to size. During the peak of the Manhattan Project, 30 to 40 homes were built in a day. The "alphabet" houses remained the property of the government until 1956, when they were sold to private owners. They were constructed of such high quality materials that many are still in use. Current residents consider it a point of pride to live in a "B" or "D" house.

Schools, businesses and stores were grouped throughout the community to create neighborhoods. Historic Jackson Square is at the heart of the original town site. Surrounded by "alphabet" houses, this attractively landscaped enclave of restaurants and shops has been expanded, remodeled and modernized over the years, but it is still a busy retail area. It also is home to the Oak Ridge Community Playhouse, the longest continually running theater in the Southeast US. Built as a movie theater, it now presents seven full-length plays, including two musicals, each year.

Nearby is the pretty little Chapel on the Hill, dedicated in 1943. Originally the community’s only house of worship, it was shared by all faiths, with services scheduled almost back to back on weekends. Catholics departed as Protestants arrived. The church continues to have an active membership.

Next to the chapel is the Alexander Inn, where many of the world’s leading scientists and top executives stayed during the early years of the Manhattan Project. Because of the emphasis on security, it was typical for guests to register under assumed names, but Enrico Fermi, J. Robert Oppenheimer and Secretary of War Henry Stimson are among those known to have slept there.

Facilities for producing fissionable material to build the bomb were located some distance from the town site and from each other. The three plants still are known by their wartime code names.

The Y-12 plant was the first facility anywhere to separate the uranium 235 isotope from natural uranium in sufficient quantity and quality to produce fissionable material for atomic weapons. It utilized an electromagnetic process developed by the University of California at Berkeley. The plant ceased uranium separation by this process in 1947, but it now is used for research and development and specialized production.

The K-25 plant separated uranium 235 by the more economical gaseous diffusion process. Approximately one mile long, it was the broadest based building in the world when it was constructed. The K-25 process was implemented as a back-up for the work being done at Y-12, which was a faster method of production. However, K-25 continued to operate long after Y-12, being shut down by the government in 1964 then reopened to service private customers into the 1970s.

The best way to view K-25 is on the Secret City Scenic Excursion Train, which offers one-hour narrated rides and dinner trips on selected dates from April through December, using restored passenger cars pulled by 1950s’ Alco diesel locomotives. The train is operated by the Southern Appalachia Railway Museum.

The third facility, X-10, housed a graphite moderated nuclear reactor and was constructed as a pilot plant for the larger plutonium production complex built in Hanford, Washington. The X-10 area became the Oak Ridge National Laboratory in 1948. The laboratory has gained international recognition for its research in basic sciences, energy systems, environmental technology and safety. The graphite moderated reactor was used to produce radioisotopes after the war and was closed in 1963. It has since been designated a National Historic Landmark and opened to the public.

Bus tours to the X-10 reactor are available from the American Museum of Science and Energy. They run Tuesday to Friday from June through September and include admission to the museum.

Some security measures remain in effect for all three Oak Ridge facilities, so visitors must provide adequate identification (preferably a valid passport) to participate in both the train excursions and bus tours.

The American Museum of Science and Energy, located next to the Welcome Center, is probably the best place to begin a visit to Oak Ridge. It contains one of the world’s largest exhibits about atomic power and other energy sources, enhanced by interactive displays and live demonstrations. The museum’s "Oak Ridge: World War II Secret City" gallery uses historic photos, documents, equipment and other artifacts to tell how the city was created, how its residents lived and worked during the war years, and how they reacted when the bomb was dropped.

Adjacent to the museum is Bissell Park, site of the annual Secret City Festival, scheduled for June 15 and 16 in 2007. The two-day event is packed with family entertainment, ranging from a children’s rides and games area to a large antiques and collectibles market to evening concerts by oldies but goodies, such as 2006's Charlie Thomas Drifters and Blood, Sweat and Tears.

But the highlights of the weekend are always the World War II battle re-enactments. In 2006, more uniformed re-enactors than ever before represented United States, British and German troops, using authentic period weapons and vehicles. The Five Oh First Group of Knoxville stages the mock battles, which have become the largest World War II re-enactments in the South.

More than 20,000 people attended the 2006 Secret City Festival, which ranks as East Tennessee’s premiere summer event.

So now the secret is out. And while Oak Ridgers today are open about the work done in their city during World War II, they like for visitors to know how that work has led to other developments which benefit modern society. For the record, Oak Ridge may be thanked for artificial hip joints, the Braille writer, dental x-ray shielding, the direct drive sewing machine motor, flu vaccines, the omni-directional wheelchair, the surgical aneurysm clip, touch screen computer technology and variable frequency microwaves, among other things.

British Columbia travel writer Toni Dabbs is a regular contributor to The Cultured Traveler.