Rachel Cosgrove (11 December 1922 – 10 October 1998), later Rachel Cosgrove Payes, was one of the Royal Historians of Oz. She wrote The Hidden Valley of Oz, one of the last of the "Famous Forty" Oz books. Her follow-up book, The Wicked Witch of Oz, was rejected by Reilly & Lee on the grounds that Oz books were no longer selling; it was published by The International Wizard of Oz Club in 1993, four decades after it was written.
Her Oz short story "Percy and the Shrinking Violet" was published in Oz-story Magazine No. 1 in 1995, while her "Spots in Oz" appeared in Oz-story No. 3 in 1997. These stories feature two of her most distinctive characters, Percy the white rat and the Leopard with the Changeable Spots.
Apart from Oz, Cosgrove Payes was a prolific author of popular fiction, especially (though not exclusively) romances, written under the pseudonym "Joanna Kaye." She wrote science fiction under the pen name "E. L. Arch" (an anagram of "Rachel"). She also wrote mysteries; she published 40 books over her full career.
A research biologist by training, Rachel Cosgrove married Norman Morris Payes in 1954. She was born in Westernport, Maryland; she died in Brick, New Jersey.
- Eric Shanower. "The Royal Historian of Oz V: A Reminiscence," The Baum Bugle, Vol. 43 No. 1 (Spring 1999).