Trapper John Johnston's body was buried in the Veterans Administration cemetery in Los Angeles, CA. After the movie came out, Johnston's body was reburied at Old Trail Town in Cody, WY. Robert Redford was a pallbearer in the reburial ceremony attended by 2,000 people.
Based upon a real-life trapper named John Johnston, nicknamed "Crow Killer" and "Liver Eater Johnston" for his penchant for cutting out and eating the livers of Crow Indians he had killed (several Crows had murdered his wife and he swore vengeance against the entire tribe).
Liver Eatin' Johnston's wife (who was pregnant at the time) was actually killed by a random raiding party of Blackfeet, not as revenge for a violation of their burial grounds. She was killed in the spring while Johnston was off trapping and he didn't return to find her body until several months later. He identified the band that had killed her because he recognized a Tennessee rifle he had given her in the possession of a Blackfeet warrior. Also, rather than isolated incidents as shown in the movie, Johnston often recruited other mountain men as well as Indians (particularly Flatheads) to help him with his vendetta. The part about the warriors sent to kill him and told not to return without his scalp was true.
According to the book "Crow Killer", the Crazy Woman was a real person who had settled in the Wolf Tail Valley. After her children were killed and her husband taken captive, she remained in her cabin. Liver Eatin' Johnson, Del Gue and Anton Sepulveda were among the mountain men who "avenged" her. One popular story was that the mountain man known as "Hatchet Jack" was actually her husband who had gone insane after being scalped and tortured by the Blackfeet when they took him away. It was known that Hatchet Jack had been scalped at some point in his life and that he was mentally unbalanced. Johnson refers to this when he tells the Crazy Woman that he cannot find any sign of her husband, but that he might return if he escaped from the Indians.
Robert Redford once said of doing his own stunts on the film: "I like the tough stuff. Half the fun of making movies is doing the action scenes. Anyone can say words. Don't get me wrong. The stunt guys are really necessary and I never do the stunts where a pro can pull it off safer and better. But I do like to do the action where the camera is too close to tell a lie and the movie's insurance men are back at the office making out policies".
Casting for the role of Swan, Jeremiah's wife, took three months. After auditioning for a role in a different film, actress Delle Bolton was spotted by the casting director. She was interviewed along with 200 Native American women and eventually won the role.
According to writer John Milius, he didn't get along with Robert Redford and Sydney Pollack and was fired. Milius claimed that subsequent writers couldn't write as he did, and the only one who made a contribution to the script was Edward Anhalt. After Anhalt left the project, Pollack and Redford rehired Milius to finish the film.
Robert Redford once said of the freezing cold temperatures on the shoot: "We had seven cases of frostbite, four cases of strep throat, two cases of pneumonia--and only three cases of Napoleon brandy! One week the thermometer didn't get up to zero once. Even the horses balked at coming out of their stalls. [Sydney Pollack] wondered where it was all going to end. I had a good idea, because I live there all year-round and know how tough a Utah winter can be. The weather couldn't have been rougher for the crew, but terrific for the finished film".
The picture was based on two published sources: the non-fiction "Crow Killer: The Saga of Liver-Eating Johnson" by Raymond W. Thorp and Robert Bunker (1958) and the fictional "Mountain Man: A Novel of Male and Female in the Early American West' (1965) by Vardis Fisher.
Not until the very end of shooting the picture did director Sydney Pollack decide the fate of what would happen to Jeremiah Johnson (Robert Redford) at the end of the film, though in reality, Redford decided.
State and national parks and forests in Utah featured in the movie included the Uinta National Forest in Provo; the Zion National Park in Springdale; the Wasatch National Forest (aka the Wasatch-Cache National Forest) in Salt Lake City; the Snow Canyon State Park in Ivins and the Ashley National Forest in Vernal.
"Fort Hawley", mentioned twice in the movie, was the actual historical Fort Hall, a well-known trading post established in 1834 along the Snake River in present-day southern Idaho. There actually was a Fort Hawley located below Fort Benton on the south side of the Missouri, 20 miles above the Musselshell River.
Principal photography began in January 1971, but unexpected changes in weather threatened production. Even after Sydney Pollack mortgaged his home to make up for budgetary constraints, production was very limited as threat of going over budget loomed. "The snows of St. George in southern Utah were terrible," said Pollack, "and we were using Cinemobiles as the lifelines. There was no way I was going to let it overrun, and [Robert Redford] was a superb partner in keeping us tight. In the end it was the greatest way to learn production, because I was playing with my own money." Struggling with weather and budgetary concerns, very rarely was there time or money to shoot any second takes.
The film took 7-1/2 months to edit. "It's a picture that was made as much in the editing room as it was in the shooting," said Sydney Pollack. 'It was a film where you used to watch dailies and everybody would fall asleep, except /Robert Redford (I)'] and I, because all you had were these big shots of a guy walking his horse through the snow. You didn't see strong narrative line. It's a picture made out of rhythms and moods and wonderful performances."
The picture was shot in Utah where Robert Redford owns a ranch and property. The state is also home to where his Sundance Film Festival is held each year. Redford's later contemporary cowboy picture, The Electric Horseman (1979), was partially shot in Utah.
The movie was made before Robert Redford's The Candidate (1972) but not released until after it, in December of 1972, to capitalize on and coincide with the publicity surrounding the 1972 US elections.
The movie features opening overture running for around three minutes and then in the middle of the film about a two minute entr'acte (French for "between the acts") intermission. The film's DVD release restores the overture and the exit music which were deleted from the home video releases.
The trivia items below may give away important plot points.
Robert Redford once said of what happens to his character at the end of the movie: "[Sydney Pollack] wanted me to freeze to death but I preferred to leave Johnson's fate up to the audience's imagination by having him disappear into the mountains". 'The Virgin Film Guide' noted that "That ambiguous fate is exactly what happened to the real Johnson".
Notoriously, influential New Yorker critic Pauline Kael based much of her review around the idea that in the final shot Johnson flips Paints-His-Shirt-Red off, as she saw the movie without her spectacles.