Before Dr. Seuss was famous he drew these sad, racist ads ... and then totally changed his mind

AP PhotoTheodor Seuss Geisel - "Dr. Seuss."

Dr. Seuss's political leanings are well known - he was a liberal Democrat who opposed fascism in the 1940s and President Nixon in the 1970s. The movie of his book The Lorax is a fairly unsubtle pro-environment allegory.

Less well celebrated are Theodor Seuss Geisel's early advertising and political cartoons from the 1920s through the 1940s, which have a racist streak.

In the ads (from the collection of the library of the University of California, San Diego), black people are presented as savages, living in the tropics, dressed in grass skirts. Arabs are portrayed as camel-riding nomads or sultans.

The images are surprising because they reveal that one of America's most original artist-authors had the same, tired views of non-whites that his contemporaries did.

More optimistically, Seuss later changed his mind and began drawing cartoons that criticised people with prejudiced ideas. Here's a look at that journey, as seen in images that never featured in his children's books.

Warning: Readers may find the following images offensive or upsetting.