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..
Ozoplaning with the Wizard of Oz
Ozoplaning with the Wizard of Oz (1939) is the thirty-third in the series of Oz books created by L. Frank Baum and his successors, and the nineteenth and last written by Ruth Plumly Thompson. It was illustrated by John R. Neill.