The film continues immediately following Back to the Future Part II (1989); while stranded in 1955 during his time travel adventures, Marty McFly (Fox) discovers that his friend Dr. Emmett "Doc" Brown (Lloyd), trapped in 1885, was killed by Buford "Mad Dog" Tannen (Wilson), Biff's great-grandfather.

Part III was released in the United States on May 25, 1990, six months after the previous installment, and grossed $245 million worldwide during its initial run, making it the sixth-highest-grossing film of 1990.

Despite the letter's warning, Marty travels back to September 2, 1885, to save Doc, arriving in the middle of a cavalry pursuit of Native Americans, but the car's fuel line is damaged in the process.

The next morning, under the alias Clint Eastwood, Marty arrives in a newly-founded Hill Valley, but runs afoul of Buford and his gang.

While inspecting a rail spur, Doc saves the town’s new schoolteacher Clara Clayton from falling into the ravine, averting her death from the original timeline.

Buford then challenges him to a showdown in two days by calling him "yellow"; an angry Marty accepts, believing that he and Doc would have left by then.

Doc passes out after downing just one shot; he is eventually revived, but is captured by Buford's gang, forcing Marty into the duel.

As Marty and Jennifer examine the DeLorean wreckage, a steam locomotive suddenly appears, operated by Doc, Clara, and their children.

Needles, as well as Marc McClure, Wendie Jo Sperber and Jeffrey Weissman as Dave, Linda and George McFly, respectively.

Hugh Gillin, Burton Gilliam, Donovan Scott and Bill McKinney portray Hill Valley's mayor, a gun salesman, Strickland's deputy, and an engineer respectively.

While Zemeckis was shooting most of the train sequences in Sonora, Gale was in Los Angeles supervising the final dub of Part II.

[9] Zemeckis would wrap photography and board a private plane to Burbank, where Gale and engineers would greet him on the dubbing stage with dinner.

The following morning, Zemeckis would drive to the Burbank Airport, board a flight back to the set in Northern California, and continue to shoot the film.

[9] Although the schedule for most of the personnel involved was grueling, the actors found the remote location for Part III relaxing, compared to shooting its predecessor.

[9] Thomas F. Wilson, who played Buford Tannen, chose to perform his own stunts and spent a great deal of time learning to ride a horse and throw his lariat.

[5] Alan Silvestri returned to compose the score for Back to the Future Part III, continuing his longtime collaboration with Zemeckis.

The photography in Part III was a "dream" for cinematographer Dean Cundey, who shared with much of the crew his excitement to shoot a Western.

He coordinated the actors, a live 4-6-0 ten wheeler steam locomotive (the Sierra Railway 3[13][14]), pyrotechnics, and special effects, and countless technicians all at once.

[15][16] On November 8, 1990, MCA/Universal Home Video released Back to the Future Part III on VHS and on December 17, 2002, on DVD.

[18][19][20] The soundtrack was released under Varèse Sarabande on May 29, 1990, and features most of the score by Alan Silvestri and the orchestral version of the song "Doubleback" performed at the festival in 1885 during the film.

The website's consensus reads: "Back to the Future Part III draws the trilogy to a satisfying close with a simpler, sweeter round of time-travel antics.

[36] The casting of Steenburgen for Back to the Future Part III appears to be deliberately intended to mirror the earlier role.

Co-writer Bob Gale commented that he did not wish to see another film in the series without the Marty McFly character nor any other actor than Michael J.

[42] In an interview on October 21, 2015, the day of Marty McFly's purported arrival in the future, Christopher Lloyd stated that he would consider making a fourth film under the condition that the original cast and creative team returned, along with a story "worth telling".

[43] The same day, Lloyd reprised his role as Doc Brown in a brief segment in which the character returns with a special message marking the 2015 date.

[44][45] In 2020, actor Tom Holland claimed in an interview with BBC Radio 1 that he was approached by an unnamed producer over a possible reboot of the franchise with him starring the lead role as Marty McFly (or a similarly new character).