His birthday is now recognized as Read Across America Day, where children all over the country celebrate their love of reading and learning.
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We're celebrating Dr. Seuss with five facts about his life you may not have known.
1. Theodor Seuss Geisel says he adopted the pen name "Dr. Seuss" because he was saving his real name for the Great American Novel he intended to write one day.
2. Dr. Seuss was not a doctor. He briefly studied English literature at Oxford after graduating from Dartmouth but instead became a cartoonist. In 1955, Dartmouth awarded him an honorary doctorate.
3. Only four of the 44 books Dr. Seuss wrote and illustrated are written in prose.
4. Dr. Seuss wrote "The Cat in the Hat" because he was concerned about kids learning to read. A publisher reportedly challenged him to "Write me a story that first-graders can't put down!"
5. Dr. Seuss has received two Emmys, a Peabody award and a Pulitzer Prize (special citation).
Happy Birthday, Dr. Seuss!