What was the event that started the space race?

The space race was a competition between the United States and the Soviet Union that lasted approximately from 1957 to 1975. It involved the parallel effort between the two countries to explore outer space with artificial satellites, to send humans into space and to pose a human being in Moon.

Although its roots lie in the early rocket technologies and international tensions that followed World War II, the space race actually began after the Soviet launch of Sputnik 1 on October 4, 1957.