Back to the Future Part III is a 1990 American science fiction comedy Western film. It is the third and final installment of the Back to the Future trilogy. The film was directed by Robert Zemeckis and starred Michael J. Fox, Christopher Lloyd, Mary Steenburgen, Thomas F. Wilson, and Lea Thompson. The film takes place immediately after the events of Back to the Future Part II. While stranded in 1955, Marty McFly discovers that his friend Dr. Emmett "Doc" Brown was killed by Biff Tannen's great-grandfather Buford. Marty decides to travel to 1885 to rescue Doc and return to his own timeline.Filming took place in both California and Arizona, and the film was released in the United States on May 25, 1990. The film was a commercial success and achieved $244.53 million at the international box office, making it 1990's sixth highest grossing film.PlotOn November 12, 1955, Marty McFly discovers that his friend Dr. Emmett "Doc" Brown has become trapped in the year 1885. Marty, with the 1955 Doc, uses the information in Doc’s 1885 letter to locate and repair the DeLorean. While retrieving the car, Marty spots a tombstone with Doc's name, dated six days after the letter. Learning that Doc was killed by Biff Tannen's great-grandfather, Buford "Mad Dog" Tannen, Marty decides to go back to 1885 to save Doc.