Area 51 is a top-secret military test and development facility, owned and operated by the US Air Force. It is located within the Nevada Test and Training Range (NTTR), 85 miles north of Las Vegas. It is operated as Detachment 3 of the Air Force Flight Test Center, headquartered at Edwards Air Force Base in California.
Area 51 was founded in 1955 to test the newly developed U-2 Spy Plane. Since then the base was constantly expanded, and used for various Black Project developments including the A-12 "Blackbird", the F-117 Stealth Fighter and the B-2 Stealth Bomber. More recent projects include research on Stealth Technology, various unmanned reconnaissance and combat aircraft (UAVs and UCAVs) and possibly a rumored high speed high altitude platform known as "Aurora".
Some believe that the research at Area 51 also includes Alien technology. However, there is no credible evidence to support such claims.