The base most likely supports development and testing of experimental aircraft and weapons systems, but its current primary purpose is publicly unknown. Although the base has never been declared a secret base, all research and occurrings in Area 51 are classified as Top Secret Information. The intense secrecy surrounding Area 51 has made it the frequent subject of conspiracy theories. The area around Area 51, including the small town of Rachel, Nevada, is a popular tourist destination.
Historically, the Groom Lake test facility was established by the Central Intelligence Agency (CIA) for Project Aquatone, which was the development of the Lockheed U-2 aircraft in 1955. Given the the extreme secrecy enveloping the project, the CIA understood that the flight test and pilot training programs could not be conducted at Edwards Air Force Base or Lockheed's Palmdale facility. A search for a suitable testing site for the U-2 was conducted under the same extreme security as the rest of the project. The lakebed of Groom Lake made an ideal strip from which they could test aircraft, and the mountain ranges about 100 miles north of Las Vegas, protected the test site from visitors.
During the Cold War, one of the missions carried out by the United States was the test and evaluation of captured Soviet fighter aircraft and Area 51 played host to an assortment of Soviet-built aircraft. The Lockheed Have Blue prototype stealth fighter first flew at Groom in December 1977 also.
Many of the hypotheses of Area 51's secretive nature concern underground facilities at Groom or at Papoose Lake that include claims of a transcontinental underground railroad system, a disappearing airstrip and engineering based on alien technology.