Filmed at the beginning of 1979, Steve McQueen was already very ill with cancer. He had difficulty breathing, and began coughing up blood towards the end of filming, but assumed he had pneumonia.
Five directors worked on this film, but were either fired or left because of disagreements with Steve McQueen. It is widely believed that McQueen directed much of the movie himself.
Steve McQueen gave up smoking cigarettes after developing a persistent cough at the end of 1978, just before filming began. He continued to smoke cigars.
In February 1980, Steve McQueen's cancer was found to have spread. On 11 March 1980, just 17 days before this film premiered, the "National Enquirer" reported that his condition was terminal.
After the Apache Wars, Tom Horn used his Chief of Scouts earnings to build his own ranch in the Galiuro Mountains near Aravaipa Canyon in Arizona. Cattle thieves robbed and burned his ranch one night. This led to his extreme hatred of cattle thieves in Wyoming.