The Mandeville Special Collections Library at UC San Diego has a special exhibit of the artwork of Dr. Seuss from before he made a living selling books when he helped other people sell things.
You may notice much of the work is signed “Dr. Seuss”, which drove me to spend a significant chunk of time reading up on Theodore Geisel and when he started using the pseudonym. If that was my rabbit hole, then that signature was my white rabbit.
It is really interesting to see versions of recognizable characters, like Horton the elephant, appear in the ads. It’s like finding old commercials done by celebrity actors when they were young (except that these ads are more good-looking and stylish than embarrassing).
*Hat tip to Neatorama.