The Apollo spaceflight program lasted from 1961 to 1972. Apollo 11 was Neil Armstrong's famous first step. Apollo 17 was the last manned mission to the moon. In all, 20 Apollo flights were planned ...

On this date, Jan. 4, 1970, NASA officially canceled the Apollo 20 mission and transferred the Saturn V rocket that would have sent astronauts to the moon to the Skylab mission.

On January 4, 1970, NASA cancelled the Apollo 20 moon mission. This came just six months after Apollo 11 astronauts Buzz Aldrin and Neil Armstrong became the first people to ever set foot on the moon.

This is a view of an astronaut's footprint on the Moon made during the Apollo II landing on July 20, 1969, by Neil Armstrong and Edwin Aldrin. (AP Photo/NASA) Splashdown!

In this photo provided by NASA, astronaut Edwin "Buzz" Aldrin poses for a photograph beside the U.S. flag deployed on the moon during the Apollo 11 mission on July 20, 1969.