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..
Queen Zixi of Ix
Queen Zixi of Ix, or The Story of the Magic Cloak, is a children's book written by L. Frank Baum and illustrated by Frederick Richardson. It was originally serialized in the early 20th-century American children's magazine "St. Nicholas" from November 1904 to October 1905, and was published in book form later in 1905 by The Century Company. The events of the book alternate between Noland and Ix, two neighboring regions to the Land of Oz, and Baum himself commented this was the best book he had written. In a letter to his eldest son, Frank Joslyn Baum, he said it was "nearer to the "old-fashioned" fairy tale than anything I have yet accomplished," and in many respects, it adheres more closely to the fairy tale structure than the Oz books.