However, Carolyn Keene was a pen name used by a team of different authors over the years. The first Hardy Boys books were written by Franklin W. Dixon, but that was also a pen name! It was used by Lester Meade, who was a writer for the Stratemeyer Syndicate, a company that created and produced popular series books for children.
So, while Carolyn Keene was the face of the Hardy Boys books, the actual writing was done by a group of authors under different pen names.