Tranquility Base (Latin: Statio Tranquillitatis) is the site on the Moon where, in July 1969, humans landed and walked on a celestial body other than Earth for the first time. On July 20, 1969, Apollo 11 crewmembers Neil Armstrong and Buzz Aldrin landed their Apollo Lunar Module Eagle at approximately 20:17:40 UTC. Armstrong exited the spacecraft six hours and 39 minutes after touchdown, followed 19 minutes later by Aldrin. The astronauts spent two hours and 31 minutes examining and photographing the lunar surface, setting up several scientific experiment packages, and collecting 47.5 pounds (21.5 kg) of dirt and rock samples for return to Earth. They lifted off the surface on July 21 at 17:54 UTC. The two named the base, which Armstrong announced when the Lunar Module Eagle landed. It is located in the south-western corner of the dark lunar plain Mare Tranquillitatis ("Sea of Tranquility").
Due to involvement of facilities within the U.S. states of California and New Mexico with the Apollo program, the relevant government bodies in these states have registered Tranquility Base as a historic site associated with the heritage of the respective state: the California State Historical Resources Commission in the California Register of Historical Resources, and the New Mexico Historic Preservation Division of the New Mexico Department of Cultural Affairs in the New Mexico State Register of Cultural Properties site #1946. However, Texas, the U.S. National Park Service, and UNESCO have declined to do so, citing the procedural technicality that it is not located within their borders (which according to common convention don't extend thousands of miles beyond the Earth's surface).