In the 1950s, there was a "Cold War." It was between the United States and the Soviet country called the U.S.S.R. We now call it Russia. These two countries were called "superpowers." The Cold War was not a real war. Each country thought it was the best. Each wanted the most power. Each of them wanted to be the first to go into space.
The Space Race began in 1955. The United States began to make a satellite. It was named Vanguard. The U.S.S.R. worked on a satellite, too. It was named Sputnik.
On October 4, 1957, the U.S.S.R. sent Sputnik I into space. It was only the size of a basketball. But it was a very big victory for the U.S.S.R.! This victory led to increased tension between the two superpowers.