The first landing on Mars will be made in 1985-1986

Boeing / NASA :
"American manned Mars expedition. Study 1968. In January 1968 Boeing issued a report that was the result of a 14 month study on manned Mars missions.
The Integrated Manned Interplanetary Spacecraft represented the culmination of a decade of NASA studies and became the starting point when manned Mars studies would resume in the 1980's. If the start of full-scale development began in 1976, the first landing on Mars could be made in 1985-1986."