The opening flashback in Indiana Jones and the Last Crusade takes place in 1912.
The sequence shows a teenage Indiana Jones attempting to recover a stolen Cross of Coronado from grave robbers in Utah. It establishes several features associated with the adult character, including his resourcefulness, fear of snakes, and distinctive use of a bullwhip.
The film then jumps forward to 1938, when the adult Indiana becomes involved in the search for the Holy Grail. His father, Henry Jones Sr., has devoted much of his life to researching the Grail, and the two are drawn into a conflict with the Nazi-sponsored expedition led by Walter Donovan.
The 1912 prologue is fictional and does not depict a real historical event. Its date is important because it presents the character at age 13 and serves as the origin story for elements later familiar from the Indiana Jones films.