The program required a remote location that wasn't easily accessible to civilians or spies. Area 51 fit the bill perfectly. It was in the Nevada desert near a salt flat called Groom Lake.

Area 51, located 120 miles outside Las Vegas, has been shrouded in a veil of secrecy since its founding in 1955, when it was established as part of the Nevada Test and Training Range complex.

It started as a bit of a joke, but now the US Air Force has told people not to go near Area 51. More than a million people have RSVP'd to an event on Facebook, threatening to storm the top-secret ...