Who wrote the Boxcar Children books after Gertrude Chandler Warner's death?

Question

Gertrude Chandler Warner's story The Boxcar Children became the first in a series of books that she continued writing until her death in 1979. She wrote a total of nineteen books in the series.

But there are more Boxcar Children books dated years after that. For example The Castle Mystery, #36 in the series, was published in 1993. On the cover of the edition published by Scholastic, it says "created by Gertrude Chandler Warner", and the same with all the books after Benny Uncovers a Mystery, the last book she wrote.

She created the series but she evidently didn't write these books since she died in 1979. However, the books don't list the actual author's name anywhere.

Books don't write themselves, so who wrote the later stories in the Boxcar Children series?

Answer 1

The publisher, Albert Whitman & Company, interviewed two of the ghostwriters for the series, Stacia Deutsch and Rhody Cohon. They are credited as "the ghostwriters behind many of The Boxcar Children books, including the recent Cupcake Caper" (#125, published 2010).

The site gives this longer biography:

Stacia Deutsch and Rhody Cohon are the #1 New York Times best-selling co-authors of more than thirty children’s books. In addition to their award winning creative chapter book series entitled, BLAST TO THE PAST (Simon and Schuster), Stacia and Rhody have also published non-fiction texts, a young adult romantic comedy called IN THE STARS (Simon and Schuster), and HOT PURSUIT, a civil rights story (Kar-Ben/Lerner). Their works have won them the Teacher’s Choice Award, the Arizona Glyph, and a SCRIBE award. Stacia and Rhody have also written several licensed properties, including NANCY DREW AND THE CLUE CREW (Simon and Schuster) and THE BOXCAR CHILDREN (Albert Whitman). They have also written junior movie tie in novels for summer blockbuster films, including BATMAN, THE DARK KNIGHT(HarperCollins) and CLOUDY WITH A CHANCE OF MEATBALLS (Simon and Schuster). Stacia Deutsch, an ordained rabbi, lives in Irvine, California with her three children. Rhody Cohon, a college math teacher, lives with her three children in Tucson, Arizona. They talk on the phone a hundred times a day.

Answer 2

Per Wikipedia:

Only the first 19 stories were written by creator Warner. Other books in the series have been written by other writers, but always feature the byline "Created by Gertrude Chandler Warner". The recent books in the series are set in the present day, whereas most of the original books were set in the 1920s and 1930s.

It seems they were not written by one person, but by groups of people trying to recreate the stories in the style of GCW. The authors were not credited except for the "Created By" line. The official website of the series says only this:

Gertrude Chandler Warner wrote the first 19 stories, but there are now more than 140 titles in The Boxcar Children® Mysteries series.

In addition, the list of Boxcar Children books on Wikipedia has two categories: written by GCW, and written by subsequent authors.

It seems it was a group effort.