On what date did Viking 1 land on Mars during the United States Bicentennial year?

Viking 1 landed on Mars on July 20, 1976, during the United States Bicentennial year.

NASA had originally planned the landing for July 4, the Bicentennial date, but the mission schedule changed. Viking 1 ultimately touched down in Chryse Planitia on July 20, exactly seven years after Apollo 11’s lunar landing. The timing still made the mission a major part of the scientific achievements associated with 1976.

Viking 1 was part of NASA’s Viking program, which sent two orbiters and landers to Mars. Its lander photographed the surface, analyzed soil, recorded weather measurements, and searched for signs of biological activity. It became the first U.S. spacecraft to land successfully on Mars and return useful surface data.

The date is sometimes mistakenly given as July 4 because of the original plan. July 20 is the actual landing date, while July 4 remains the date most strongly associated with the Bicentennial itself.