Viking 1 made the first successful landing on Mars during the United States Bicentennial year.
The Viking 1 lander touched down at Chryse Planitia on July 20, 1976. Its landing had originally been planned for July 4, the date of the United States Bicentennial, but images showed that the first selected site was too rough, so NASA delayed the landing while searching for a safer location.
Viking 1 was part of NASA’s Viking program and traveled with an orbiter and a lander. The orbiter entered Mars orbit on June 19, 1976, before the lander separated and descended to the surface. The spacecraft photographed the planet, studied its atmosphere and soil, and conducted biological experiments.
Viking 2 followed with its own landing on September 3, 1976. Viking 1 is sometimes confused with Mariner 9, which became the first spacecraft to orbit Mars in 1971, but it was Viking 1 that achieved the first successful landing.