Theodor Seuss Geisel—who was born in Springfield, Massachusetts on March 2, 1904—wasn't actually a doctor (at least not until his alma mater, Dartmouth, gave him an honorary PhD), but his unique poetic meter and leap-off-the-page illustrations made him one of the most successful children's writers in history. Here's a little background on some of his greatest hits.

1. THE LORAX

The Lorax is widely recognized as Dr. Seuss's take on environmentalism and how humans are destroying nature. Groups within the logging industry weren't very happy about it and later sponsored The Truax—a similar book, but from the logging point of view. Another interesting fact: The Lorax used to contain the line, "I hear things are just as bad up in Lake Erie," but 14 years after the book was published, the Ohio Sea Grant Program wrote to Seuss and told him how much the conditions had improved and implored him to take the line out. Dr. Seuss agreed and said that it wouldn't be in future editions.

2. THE CAT IN THE HAT

Dr. Seuss wrote The Cat in the Hat because he thought the famous Dick and Jane primers were insanely boring. Because kids weren't interested in the material, they weren't exactly compelled to use it repeatedly in their efforts to learn to read. So, The Cat in the Hat was born. "I have great pride in taking Dick and Jane out of most school libraries," the author once said. "That is my greatest satisfaction."

3. GREEN EGGS AND HAM

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Bennett Cerf, Dr. Seuss's editor, bet him that he couldn't write a book using 50 words or less. The Cat in the Hat was pretty simple, after all, and it used 225 words. Not one to back down from a challenge, Geisel started writing and came up with Green Eggs and Ham—which uses exactly 50 words.

The 50 words, by the way, are: a, am, and, anywhere, are, be, boat, box, car, could, dark, do, eat, eggs, fox, goat, good, green, ham, here, house, I, if, in, let, like, may, me, mouse, not, on, or, rain, Sam, say, see, so, thank, that, the, them, there, they, train, tree, try, will, with, would, you.

4. HORTON HEARS A WHO!

The line from the book "A person's a person, no matter how small" has been used as a slogan for pro-life organizations for years. It's often questioned whether that was Seuss's intent in the first place, but when he was still alive, he threatened to sue a pro-life group unless they removed his words from their letterhead. Karl ZoBell, the attorney for Dr. Seuss's interests, says the author's widow doesn't like people to "hijack Dr. Seuss characters or material to front their own points of view."

5. MARVIN K. MOONEY WILL YOU PLEASE GO NOW!

It's often alleged that Marvin K. Mooney Will You Please Go Now! was written specifically about Richard Nixon, but the book came out only two months after the whole Watergate scandal. Which makes it unlikely that the book could have been conceived of, written, edited, and mass-produced in such a short time; also, Seuss never admitted that the story was originally about Nixon.

But that's not to say he didn't understand how well the two flowed together. In 1974, he sent a copy of Marvin K. Mooney to his friend, Art Buchwald, at The Washington Post. In it, he crossed out "Marvin K. Mooney" and replaced it with "Richard M. Nixon," which Buchwald reprinted in its entirety. Oh, and one other tidbit: This book contains the first-ever reference to "crunk," although its meaning is a bit different than today's crunk.

6. YERTLE THE TURTLE

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Yertle the Turtle = Hitler? Yep. If you haven't read the story, here's a little overview: Yertle is the king of the pond, but he wants more. He demands that other turtles stack themselves up so he can sit on top of them to survey the land. Mack, the turtle at the bottom, is exhausted. He asks Yertle for a rest; Yertle ignores him and demands more turtles for a better view. Eventually, Yertle notices the moon and is furious that anything dare be higher than himself, and is about ready to call for more turtles when Mack burps. This sudden movement topples the whole stack, sends Yertle flying into the mud, and frees the rest of the turtles from their stacking duty.

Dr. Seuss actually said Yertle was a representation of Hitler. Despite the political nature of the book, none of that was disputed at Random House—what was disputed was Mack's burp. No one had ever let a burp loose in a children's book before, so it was a little dicey. In the end, obviously, Mack burped.

7. THE BUTTER BATTLE BOOK

The Butter Battle Book was pulled from the shelves of libraries for a while because of the reference to the Cold War and the arms race. Yooks and Zooks are societies who do everything differently. The Yooks eat their bread butter-side up and the Zooks eat their bread butter-side down. Obviously, one of them must be wrong, so they start building weapons to outdo each other: the "Tough-Tufted Prickly Snick-Berry Switch," the "Triple-Sling Jigger," the "Jigger-Rock Snatchem," the "Kick-A-Poo Kid," the "Eight-Nozzled Elephant-Toted Boom Blitz," the "Utterly Sputter," and the "Bitsy Big-Boy Boomeroo."

The book concludes with each side ready to drop their ultimate bombs on each other, but the reader doesn't know how it actually turns out.

8. AND TO THINK THAT I SAW IT ON MULBERRY STREET

Dr. Seuss's first children's book, And to Think That I Saw It on Mulberry Street, was rejected 27 times according to Guy McLain of the Springfield Museum in Geisel's hometown. Only after Geisel bumped into a friend who'd just been hired by a publishing house did the book get the green light. "He said if he had been walking down the other side of the street," McLain told NPR, "he probably would never have become a children's author."

9. OH, THE PLACES YOU'LL GO!

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Oh, The Places You'll Go! is Dr. Seuss's final book, published in 1990. It sells about 300,000 copies every year because so many people give it to college and high school grads.

10. HOW THE GRINCH STOLE CHRISTMAS!

No Dr. Seuss story would be complete without a mention of the television special based on his book How the Grinch Stole Christmas! In the Dr. Seuss-sanctioned cartoon, Frankenstein's Monster himself, Boris Karloff, provided the voice of the Grinch and the narration. Seuss was a little wary of casting him because he thought his voice would be too scary for kids.

Tony the Tiger, a.k.a. Thurl Ravenscroft, is the voice behind "You're a Mean One, Mr. Grinch." He received no credit on screen, so Dr. Seuss wrote to newspaper columnists to tell them exactly who had sung the song.

An earlier version of this article ran in 2009.