Oak Ridge was one of the “Secret Cities” of the Manhattan Project. Three sites for Uranium enrichment and a city of 70,000 were built into a quickly evicted area of East Tennessee. Roads and community names disappeared from the maps. Anybody living and working at the Clinton Engineer Works had a badge and was controlled when entering. The city was opened in 1949 and the city gates were removed, but a new set of permanent checking stations was constructed at the access roads to the plants. These guard houses are single-story main buildings with two-story guard towers at one corner and a smaller one-story guard house across the street, all including gun portals and bulletproof glass. The gates were only in commission until 1953, then the checkpoints moved. DOE renovated two of them and they are on the National Register of Historic Places now.