NASA: Apollo Missions

On May 25, 1961, President John F. Kennedy announced the goal of sending astronauts to the moon before the end of the decade. The National Aeronautics and Space Administration (NASA) met that challenge with the Apollo Program, which ran from 1968 to 1972. Apollo consisted of 17 manned flights with the ultimate goal of landing on the moon.
The first 10 Apollo flights tested various mission elements. Launched on July 16, 1969, Apollo 11 and its crew of three astronauts traveled to the moon. On July 20, Neil Armstrong and Buzz Aldrin boarded a landing craft and descended to the surface, becoming the first to ever do so. Armstrong and Aldrin remained on the moon for just over 21 hours, and only spent two and a half of those outside the spacecraft. During this time they set up several experiments and collected samples for later study. After reuniting with their fellow astronaut, Michael Collins, in orbit, the three returned to Earth, splashing down in the Pacific Ocean on July 24.
Six more missions (Apollo 12-17) followed, each mission remained on the moon for consecutively longer periods of time. Apollo 13, which suffered a mechanical failure that forced its return, was the only other mission that did not land on the moon.
Additional Resources:

• Apollo Program: 40th Anniversary
• Images of Apollo Landing Sites
• Kennedy Space Center: Apollo Program Overview
• Restored Videos from Apollo 11 Moonwalk
• We Choose the Moon: Apollo 11 Mission Replay
• NASA: History
• NASA: Lunar Exploration Missions