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
Baum dedicated the book "to my good friend & comrade, My Wife," Maud Gage Baum. In January 1901, George M. Hill Company completed printing the first edition, a total of 10,000 copies, which quickly sold out. "The Wonderful Wizard of Oz" sold three million copies by the time it entered the public domain in 1956.