Atlas, it's almost as old as the B-52.
Atlas has had a long and illustrious history, beginning in the 1950s. It was designed to be America's first ICBM in the arms race with the Soviet Union. It was retired from that role in 1965, having been superseded by more advanced Titan II and Minuteman missiles. Even before then, though, it was pressed into service as a space launch vehicle. It launched America's first astronauts in Project Mercury, as well as a variety of satellites and space probes using Agena and Centaur upper stages. Among its famous firsts were Mariner 2, the first flyby of Venus; Mariner 4, the first flyby of Mars; and Pioneer 10 and 11, the first flybys of Jupiter and Saturn and the first man-made objects to leave the solar system. It was steadily upgraded, enlarged, and improved over the years, and became known for its reliability.
The Atlas V, however, is an entirely new rocket that has nothing in common with the earlier versions. It first flew in 2002 and is available in a variety of configurations for different missions. Ironically, it uses a Russian-designed first stage engine.
Atlas familyAtlas V