Sputnik was the first of several satellites in the Soviet Union's Sputnik program, the majority of them successful. Sputnik 2 followed as the second satellite in orbit, also the first to carry an animal, the dog Laika. The first failure occurred with Sputnik 3.
The United States had also been working on satellites, primarily through teams working for the US Navy as Project Vanguard. Their first launch had originally been intended to launch before Sputnik, but was delayed several times before blowing up on the pad. A rush effort then started under the US Army's Jupiter project and succeeded launching Explorer I in January 1958. This is considered the start of the Space Race between the two superpowers, as an aspect of the Cold War. Both nations attempted to outdo each other in space exploration, eventually culminating in the launch of the Apollo 11 mission to the Moon. Sputnik 1 fell back to Earth on January 4, 1958.
In 2003 a back-up unit of Sputnik 1 called "model PS-1" was sold on eBay (minus the classified military radio part that were removed in the 1960s). It had been on display in a science institute near Kiev. It is estimated that between four and twenty models were made for testing and other purposes.