Vanguard 1

Vanguard 1 was the fourth artificial Earth orbit satellite launched into space. It was placed into orbit on 17 March 1958 from Cape Canaveral, Florida. Vanguard 1, the world’s first solar-powered satellite, was designed to test the launch capabilities of a three-stage launch vehicle and the effects of the environment on a satellite and its systems in Earth orbit. Vanguard 1 was the second U.S. satellite in orbit, following Explorer 1, and remains the oldest artificial object orbiting Earth to this day. Though communications with the satellite were lost in 1964, it and its upper rocket stage remain in orbit and are actively tracked by NORAD. Vanguard began as a program at the Naval Research Laboratory in Washington and transferred over to NASA (along with many of its personnel) after the agency was founded by the National Aeronautics and Space Act of 1958.

https://www.nasa.gov/content/vanguard-satellite-1958