Mars Pathfinder, the second mission under NASA's Discovery Program, is the first successful US mission to Mars since the Viking probes of the 1970s. It landed on Ares Vallis, Chryse Planitia on 1997-Jul-4. It also carried
Sojourner, the first rover to move on the Martian surface.
The spacecraft operated on the surface for 85 days, until contact was lost on the lander on 1997-Sept-27. It was believed Sojourner was still operating at the time until as late as 1997-Oct-7, but it cannot make contact with Earth directly.
The technology used on this mission became the basis of almost all later surface probes by NASA in the next 20 years (MPL, MER-A/B, Phoenix, and InSight)