Bus Stop was based on the 1955 play of the same title (which in turn was expanded from an earlier, one act play People in the Wind) by William Inge. The inspiration for the play came from people Inge met in Tonganoxie, Kansas.
Bus Stop was the first film that Monroe chose to make under a new contract. For the role, she learned an Ozark accent, chose costumes and make-up that lacked the glamour of her earlier films, and provided deliberately mediocre singing anddancing. Joshua Logan, known for his work on Broadway, agreed to direct, despite initially doubting Monroe's acting abilities and knowing of her reputation for being difficult. The filming took place in Idaho and Arizona in early 1956, with Monroe "technicallyin charge" as the head of MMP (Marilyn Monroe Productions, her film production company), occasionally making decisions on cinematography and with Logan adapting to her chronic tardiness and perfectionism.
The experience changed Logan's opinion of Monroe, and he later compared her to Charlie Chaplin in her ability to blend comedy and tragedy.
Source: Wikipedia. Pictures: Milton Greene.