When
L. Frank Baum died in 1920,
Reilly & Lee, his
publisher, continued the Oz series, releasing a new book each year until the
1940's. There are more post-Baum works than Baum works, but because they were published by Reilly & Lee they are considered "
canonical" or "official" Oz books. Many of these official authors, or "Royal Historians of Oz," also released "non-canonical" Oz books through other publishers, once Reilly & Lee discontinued the series.
Ruth Plumly Thompson
John R. Neill
Jack Snow
Rachel R. Cosgrove
Eloise Jarvis McGraw and
Lauren McGraw Wagner