Apollo 11 was the first manned space mission to land on the Moon. It was the fifth human spaceflight of Project Apollo and the third human voyage to the Moon.
Launched on 16 July 1969, it carried Mission Commander Neil Alden Armstrong, Command Module Pilot Michael Collins and Lunar Module Pilot Edwin Eugene 'Buzz' Aldrin Jr. On 20 July, Armstrong and Aldrin became the first humans to walk on the Moon, while Collins orbited above.
The mission fulfilled President John F Kennedy's goal of reaching the moon by the end of the 1960s, which he expressed during a speech given before a joint session of Congress on 25 May 1961:
'I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth.'
Kennedy had just been humiliated in the Bay of Pigs fiasco in Cuba, a communist ally of Moscow. In his speech, he called for many measures to combat communism, requesting billions, for example, to stop red insurgencies in Southeast Asia.
But in his address, Kennedy chose space as the main Cold War battleground on which to marshal his forces. The Soviet Union opened the final frontier when it sent the Sputnik satellite into orbit in 1957. 
Four years later, cosmonaut Yuri Gagarin became the first man in space. The Soviets were beating the Americans to every milestone off the planet.
Feeling a sense of urgency in finding a way to overtake the Soviets in the space race, Kennedy had huddled with Vice President Lyndon Johnson and his science advisers to come up with a plan.
The president determined that safely landing a man on the moon would be technologically daunting, but it was a goal that the US could reach before the Soviet Union.
'No single space project in this period will be more impressive to mankind, or more important for the long-range exploration of space; and none will be so difficult or expensive to accomplish,' Kennedy said.
The president cautioned Congress that the cost would be significant, more than $9bn in 1960s dollars. Congress accepted the challenge.
Kennedy's vision guided NASA's human space flight program from the beginning. Mercury, Gemini and Apollo missions were designed with his objective in mind.
Each crewmember of Apollo 11 had made a spaceflight before this mission, making it the second all-veteran crew in manned spaceflight history.
A Saturn V launched Apollo 11 from the Kennedy Space Center on 16 July 1969 at 2.32pm Irish time.
It entered orbit 12 minutes later. After one and a half orbits, the S-IVB third-stage engine pushed the spacecraft onto its trajectory toward the Moon with the Trans Lunar Injection burn.
About 30 minutes later the command/service module pair separated from this last remaining Saturn V stage and docked with the lunar module still nestled in the Lunar Module Adaptor.
On 19 July, Apollo 11 passed behind the Moon and fired its service propulsion engine to enter lunar orbit. In the thirty orbits that followed, the crew saw passing views of their landing site in the southern Sea of Tranquility (Mare Tranquillitatis) about 20km southwest of the crater Sabine D.
The landing site was selected in part because it had been characterised as relatively flat and smooth by the automated Ranger 8 and Surveyor 5 landers along with the Lunar Orbiter mapping spacecraft and unlikely to present major landing or extra-vehicular activity (EVA) challenges.
On 20 July 1969 the lunar module Eagle separated from the command module Columbia. Collins, alone aboard Columbia, inspected Eagle as it pirouetted before him to ensure the craft was not damaged.
As the descent began, Armstrong and Aldrin found that they were passing landmarks on the surface 4 seconds early and reported they were 'long'. They would land miles west of their target point.
When Armstrong again looked outside, he saw that the computer's landing target was in a boulder-strewn area just north and east of a 400m diameter crater (later determined to be 'West crater', named for its location in the western part of the originally planned landing ellipse).
Armstrong took semi-automatic control and with Aldrin calling out altitude and velocity data, landed at 9.17pm (Irish) on 20 July with about 25 seconds of fuel left.
At 3.56am on 21 July 1969 (Irish time, still 20 July in the US), Armstrong made his descent to the Moon's surface and spoke his famous line 'That's one small step for [a] man, one giant leap for mankind' exactly six and a half hours after landing. Aldrin joined him, describing the view as 'Magnificent desolation.'
The landing drew the largest television audience for any live event up until that time.
Steven Dick, NASA's chief historian, said much later that a thousand years from now, that step might be considered the crowning achievement of the 20th century.
