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..
The Wonderful Wizard of Oz
"The Wonderful Wizard of Oz" has been adapted to other media numerous times, most famously in "The Wizard of Oz", the 1939 film starring Judy Garland, Ray Bolger, Jack Haley, and Bert Lahr. Until this version, the book had inspired a number of now less well known stage and screen adaptations, including a profitable 1902 Broadway musical and three silent films. The 1939 film was considered innovative because of its songs, special effects, and revolutionary use of the new Technicolor.