In 1938 when she was sixteen, Garland was cast as the young Dorothy Gale in "The Wizard of Oz" (1939), a film based on the 1900 children's book by L. Frank Baum. In the film, she sang the song with which she would be constantly identified afterward, "Over the Rainbow". Although producers Arthur Freed and Mervyn LeRoy had wanted to cast her in the role from the beginning, studio chief Mayer first tried to borrow Shirley Temple from 20th Century Fox, but they declined. Deanna Durbin was then asked, but was unavailable; this resulted in Garland being cast.