After the Soviet Union successfully launched space as the first artificial satellite in orbit, the United States had two concurrent programs to launch their own. One of those programs was the Vanguard program.
The first Vanguard launch was originally set for September of 1957, but because of delays, the Sputnik 1 satellite of the Soviet Union became the first artificial satellite to orbit our planet on October 4th. The first attempted launch of a Vanguard satellite into orbit ended in a spectacular failure, exploding on the pad.
Vanguard 1 would end up being the second artificial satellite of the United States of America to orbit the earth, beaten by another American satellite, Explorer 1. Vanguard 1 was launched on March 17th, 1958. The satellite returned scientific data for several years through 1964.
Remarkably, unlike many other early satellites, Vanguard 1 is still in orbit around the Earth, although no longer functional.