The Apollo program was the American spaceflight endeavor which landed the first humans on Earth's Moon. Conceived during the presidency of Dwight D. Eisenhower and conducted by NASA, Apollo began in earnest after President John F. Kennedy's May 25, 1961 special address to a joint session of Congress declaring a national goal of "landing a man on the Moon" by the end of the decade.
This goal was accomplished with the Apollo 11 mission on July 20, 1969 when astronauts Neil Armstrong and Buzz Aldrin landed on the Moon, while Michael Collins remained in lunar orbit. Five subsequent Apollo missions also landed astronauts on the Moon, the last in December 1972. In these six Apollo spaceflights, 12 men walked on the Moon. These are the only times humans have landed on another celestial body.
The Apollo program ran from 1961 until 1975, and was the US civilian space agency's third human spaceflight program (following Mercury and Gemini). Apollo used Apollo spacecraft and Saturn launch vehicles, which were later used for the Skylab program and the joint American-Soviet Apollo-Soyuz Test Project. These subsequent programs are thus often considered part of the Apollo program.
The program was accomplished with only two major setbacks: The first was the Apollo 1 launchpad fire that resulted in the deaths of astronauts Gus Grissom, Ed White and Roger Chaffee; the second was an oxygen tank rupture on Apollo 13 during the Moonward phase of its journey, which disabled the command spacecraft. Using the lunar module as a "lifeboat", the three astronauts aboard narrowly escaped with their lives, thanks to the efforts of flight controllers, project engineers, backup crew members and the skills of the astronauts.
Apollo set major milestones in human spaceflight. It stands alone in sending manned missions beyond low Earth orbit; Apollo 8 was the first manned spacecraft to orbit another celestial body, while Apollo 17 marked the last Moonwalk and the last manned mission beyond low Earth orbit. The program spurred advances in many areas of technology incidental to rocketry and manned spaceflight, including avionics, telecommunications, and computers. Apollo sparked interest in many fields of engineering and left many physical facilities and machines developed for the program as landmarks. Many objects and artifacts from the program are on display at locations throughout the world, notably in the Smithsonian's Air and Space Museums.