In 1942, a patch of isolated farm land in Tennessee was chosen as a site for a project so secret [it has been credited as](http://www.wilsoncenter.org/event/the-manhattan-project-and-its-cold-war-legacy) “the birth of the national security state”. On the land, US Army engineers built a town – given the innocuous name of Oak Ridge – according to [a master plan by the architectural firm Skidmore, Owings and Merrill (SOM)](http://www.som.com/projects/oak_ridge_new_town_master_plan). It didn’t appear on any maps. The entire town, with a population of 75,000, was fenced in and secured by armed guards – because alongside prefabricated homes, schools, and shops, there were facilities designed to refine uranium ore. Part of the Manhattan Project, which created the first atomic bombs during World War II, [Oak Ridge has just been given National Park status](http://www.latimes.com/travel/deals/la-trb-manhattan-project-national-historic-park-20141226-story.html). It was one of the architects’ more unusual projects: they had to plan their secret city with no more than an aerial contour map to work from. Civil engineer Walter G Metschke, who worked on the project, [wrote in his memoir](http://digital-libraries.saic.edu/cdm/compoundobject/collection/caohp/id/8498/rec/1): “I was told that a housing project was to be built somewhere, we didn’t know where, and that we were invited to submit a preliminary plan for three thousand single-family units… We had positively no notion as to why we were building a town with a population of seventy-five thousand.” (Credit: Chicago History Museum/Getty Images)