 The film , set in the early 1950s , is based on Donn Pearce 's 1965 novel of the same name . Pearce sold the story to Warner Bros. , who then hired him to write the script . Due to Pearce 's lack of film experience , the studio added Frank Pierson to rework the screenplay . Newman 's biographer Marie Edelman Borden states that the " tough , honest " script drew together threads from earlier movies , especially Hombre , Newman 's earlier film of 1967 . The film has been cited by Roger Ebert as an anti @-@ establishment film which was shot during the time of the Vietnam War , in which Newman 's character endures " physical punishment , psychological cruelty , hopelessness and equal parts of sadism and masochism . " His influence on his prison mates and the torture that he endures is compared to that of Jesus , and Christian symbolism is used throughout the film , culminating in a photograph superimposed over crossroads at the end of the film in comparison to the crucifixion . Filming took place on the San Joaquin River Delta , and the set , imitating a southern prison farm , was built in Stockton , California . The filmmakers sent a crew to Tavares Road Prison in Tavares , Florida , to take photographs and measurements . 
