When did we first land a spacecraft on Mars?

The Viking landers were the first spacecraft to land on Mars in the 1970s. Viking 1 and Viking 2 each had both an orbiter and a lander. On July 20, 1976 the Viking 1 Lander separated from the Orbiter and touched down on the surface of Mars. Less than two months later, on September 3, 1976, the Viking 2 lander touched down on Mars. These two landers took images of the Martian surface, studied soil samples, and studied the atmosphere of Mars.