After Indiana Jones and the Temple of Doom was criticized for its darker and more violent tone, Steven Spielberg decided to make Indiana Jones and the Last Crusade much more light and jovial. To that end, Spielberg and series co-creator George Lucas poured over countless scripts from nearly a half-dozen writers - from Chris Columbus, who had written Gremlins to Jeffrey Boam, who wrote the film’s final script.
Spielberg, who had turned down the opportunity to direct both Big and Rain Man to direct The Last Crusade, wanted to be sure the film evoked Raiders of the Lost Ark, not Temple of Doom, which is why it took so long to find a great script. However, after he and Lucas agreed on Boam’s script (after significant input from Spielberg, who suggested that Indy and his father’s relationship would be a great metaphor for the search for the Holy Grail).
Shooting began in earnest in Spain and continued in countries all across the world - including Germany, Austria, the United States, the United Kingdom. Many people who worked on the film have said that was one of the most difficult shoots of their career. Regardless, the film turned out exceptionally well thanks to a good script and Spielberg’s deft direction.