Claim: The Wizard of Oz is based on a book.

Dorothy Gale is the fictional main protagonist of many of the Oz novels by the American author L. Frank Baum . Her best friend is Oz 's ruler Princess Ozma . Dorothy first appears in Baum 's classic children 's novel The Wonderful Wizard of Oz and reappears in most of its sequels . In addition , she is the main character in various adaptations , notably the classic 1939 movie adaptation of the book , The Wizard of Oz .   In later books , Oz steadily becomes more familiar to her than her homeland of Kansas . Indeed , Dorothy eventually goes to live in an apartment in the Emerald City 's palace but only after her Aunt Em and Uncle Henry have settled in a farmhouse on its outskirts , unable to pay the mortgage on their house in Kansas . Dorothy 's best friend Princess Ozma officially makes her a princess of Oz later in the book series .