During the Cold War, the United States and the Soviet Union competed to prove their scientific and military superiority and thereby, the supremacy of democracy or communism. The Soviets took an early lead by launching Sputnik in October 1957.  This artificial satellite -- the first ever to orbit the Earth -- was a game-changer as the U.S. had underestimated the USSR's capabilities. It also stoked fears that the Soviets could launch ballistic missiles with nuclear weapons aimed at North America. More positively, it led to the creation of the National Aeronautics and Space Administration (NASA).

By January 1958, the U.S. had launched its own satellite, Explorer I. Soon thereafter however, the homegrown efforts were soon eclipsed by the Soviets when Yuri Gagarin became the first human in space, orbiting the Earth in April 1961. A month later, President John Kennedy declared that the U.S. would send a man to the moon:

"...[T]his nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon... No single space project in this period will be more impressive to mankind... and none will be so difficult or expensive to accomplish." Progress was made when Alan Shepard became the first American in space in May 1961 and again when John Glenn became the first American to orbit the Earth in February 1962 (earning him a massive New York City ticker tape parade).

And when Neil Armstrong set foot on the moon -- the first human to do so -- in July 1969, President Kennedy's vision was realized. After that, the space race slowed and the two countries turned to joint ventures in space, such as the International Space Station.