How many U.S. astronauts have walked on the Moon?

Twelve astronauts have walked on the Moon, all via Apollo lunar aircraft. Each of the six Apollo flights, which took place between 1969 and 1972, had a crew of three. However, since one crew member remained in orbit in the command service module (CSM), the other two actually stepped onto the Moon. When Neil Armstrong became the first astronaut in history to walk on the Moon on July 20, 1969, he said, “That's one small step for [a] man, one giant leap for mankind.”