Copyright status of The Wizard of Oz and related works in the United States
"The Wonderful Wizard of Oz" was published in 1900, and was the first to enter the public domain in "1956". This allowed Reilly & Lee, the publisher of all the other Oz books (as well as Baum's other books) to issue their own edition of "The Wizard of Oz", which had previously been published by George M. Hill Company and later by the Bobbs Merill Company after Hill went bankrupt..
Land of Oz
A legend of uncertain validity is that when relating bedtime stories (the earliest form of the Oz books) Baum was asked by his niece, Ramona Baxter Bowden, the name of the magical land. He glanced at a nearby filing cabinet, which had three drawers, labeled A–G, H–N, and O–Z. Thus he named the land Oz. This story was first told in 1903, but his wife always insisted that the part about the filing cabinet was not true. In "Dorothy and the Wizard in Oz", the name is translated as "great and good". It has also been speculated that Oz was named after the abbreviation for ounce, in the theory that Oz is an allegory for the populist struggle against the illusion (the wizard) of the gold standard.