The U.S. for the first time is acknowledging the location of a secretive aerial surveillance test site that conspiracy theorists have long claimed might be the home for extraterrestrials who have invaded the country.

In declassified documents disclosed this week, the Central Intelligence Agency showed a map of the remote Area 51 site in the western state of Nevada, about 80 miles northwest of the well-known gambling mecca of Las Vegas.

The CIA said it used the nearly 930-square-mile site from 1954 to 1974 as testing grounds for the government’s U-2 and Oxcart aerial surveillance programs. The U.S. deployed U-2 planes, flying at an altitude of 11 miles, around the world at the height of the Cold War, including over the Soviet Union.

The CIA document released by the National Security Archive at George Washington University in Washington traced the history of the aircraft testing. It made no mention of the facility’s role since 1974, although the government is believed to be using it for testing intelligence tools and weapons.

The report said the high-altitude U-2 tests led to an unexpected side effect — a huge increase in reports of unidentified flying objects. At the time, government officials attributed the UFO sightings to natural phenomena.

But conspiracy theorists in the U.S. have long remained skeptical of governmental pronouncements about the site. Tales of alien landings, time travel and meetings with extraterrestrials and other exotic theories about Area 51 have for years played a role in popular American movies, fostering even more curiosity about the site.

The U-2 played a prominent role in one of the Cold War’s most celebrated incidents, when the Soviets shot down American spy pilot Gary Powers in 1960. He was convicted of espionage against the Soviet Union, but eventually returned to the U.S. in an exchange of spy prisoners between the two countries.