President John F. Kennedy speaking before Congress in May 25, 1961
If we are to win the battle that is now going on around the world between freedom and tyranny, the dramatic achievements in space which occurred in recent weeks should have made clear to us all, as did the Sputnik in 1957, the impact of this adventure on the minds of men everywhere, who are attempting to make a determination of which road they should take. Since early in my term, our efforts in space have been under review. With the advice of the Vice President, who is Chairman of the National Space Council, we have examined where we are strong and where we are not, where we may succeed and where we may not. Now it is time to take longer strides - time for a great new American enterprise - time for this nation to take a clearly leading role in space achievement, which in many ways may hold the key to our future on earth. (...) 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. - John F. Kennedy
On May 25, 1961, President John F. Kennedy announced before a special joint session of Congress the dramatic and ambitious goal of sending an American safely to the Moon before the end of the decade.
A number of political factors affected Kennedy's decision and the timing of it. In general, Kennedy felt great pressure to have the United States "catch up to and overtake" the Soviet Union in the "space race."
Four years after the Sputnik shock of 1957, the cosmonaut Yuri Gagarin had become the first human in space on April 12, 1961, greatly embarrassing the U.S. While Alan Shepard became the first American in space on May 5, he only flew on a short suborbital flight instead of orbiting the Earth, as Gagarin had done. In addition, the Bay of Pigs fiasco in mid-April put unquantifiable pressure on Kennedy. He wanted to announce a program that the U.S. had a strong chance at achieving before the Soviet Union.
After consulting with Vice President Johnson, NASA Administrator James Webb, and other officials, he concluded that landing an American on the Moon would be a very challenging technological feat, but an area of space exploration in which the U.S. actually had a potential lead.
Thus the cold war is the primary contextual lens through which many historians now view Kennedy's speech. The decision involved much consideration before making it public, as well as enormous human efforts and expenditures to make what became Project Apollo a reality by 1969. Only the construction of the Panama Canal in modern peacetime and the Manhattan Project in war were comparable in scope.
NASA's overall human spaceflight efforts were guided by Kennedy's speech. Projects Mercury (at least in its latter stages), Gemini, and Apollo were all designed to execute Kennedy's goal. His goal was achieved on July 20, 1969, when Apollo 11 commander Neil Armstrong stepped off the Lunar Module's ladder and onto the Moon's surface.
Article & image source NASA