Theodor Seuss Geisel ( March 2, 1904 – September 24, 1991) was an American children's author and cartoonist. He is known for his work writing and illustrating more than 60 books under the pen name Dr. Seuss (/su?s, zu?s/ sooss, zooss). His work includes many of the most popular children's books of all time, selling over 600 million copies and being translated into more than 20 languages by the time of his death.

Geisel adopted the name "Dr. Seuss" as an undergraduate at Dartmouth College and as a graduate student at Lincoln College, Oxford. He left Oxford in 1927 to begin his career as an illustrator and cartoonist for Vanity Fair, Life, and various other publications. He also worked as an illustrator for advertising campaigns, including for FLIT and Standard Oil, and as a political cartoonist for the New York newspaper PM. He published his first children's book And to Think That I Saw It on Mulberry Street in 1937. During World War II, he took a brief hiatus from children's literature to illustrate political cartoons, and he worked in the animation and film department of the United States Army.

After the war, Geisel returned to writing children's books, writing acclaimed works such as If I Ran the Zoo (1950), Horton Hears a Who! (1955), The Cat in the Hat (1957), How the Grinch Stole Christmas! (1957), Green Eggs and Ham (1960), One Fish, Two Fish, Red Fish, Blue Fish (1960), The Sneetches and Other Stories (1961), The Lorax (1971), The Butter Battle Book (1984), and Oh, the Places You'll Go! (1990). He published over 60 books during his career, which have spawned numerous adaptations, including eleven television specials, five feature films, a Broadway musical, and four television series.

He received two Primetime Emmy Awards for Outstanding Children's Special for Halloween Is Grinch Night (1978) and Outstanding Animated Program for The Grinch Grinches the Cat in the Hat (1982). In 1984, he won a Pulitzer Prize Special Citation. His birthday, March 2, has been adopted as the annual date for National Read Across America Day, an initiative focused on reading created by the National Education Association.

Geisel left Oxford without earning a degree and returned to the United States in February 1927, where he immediately began submitting writings and drawings to magazines, book publishers, and advertising agencies. Making use of his time in Europe, he pitched a series of cartoons called Eminent Europeans to Life magazine, but the magazine passed on it. His first nationally published cartoon appeared in the July 16, 1927, issue of The Saturday Evening Post. This single $25 sale encouraged Geisel to move from Springfield to New York City. Later that year, Geisel accepted a job as writer and illustrator at the humor magazine Judge, and he felt financially stable enough to marry Palmer. His first cartoon for Judge appeared on October 22, 1927, and Geisel and Palmer were married on November 29. Geisel's first work signed "Dr. Seuss" was published in Judge about six months after he started working there.

In early 1928, one of Geisel's cartoons for Judge mentioned Flit, a common bug spray at the time manufactured by Standard Oil of New Jersey. According to Geisel, the wife of an advertising executive in charge of advertising Flit saw Geisel's cartoon at a hairdresser's and urged her husband to sign him. Geisel's first Flit ad appeared on May 31, 1928, and the campaign continued sporadically until 1941. The campaign's catchphrase "Quick, Henry, the Flit!" became a part of popular culture. It spawned a song and was used as a punch line for comedians such as Fred Allen and Jack Benny. As Geisel gained notoriety for the Flit campaign, his work was in demand and began to appear regularly in magazines such as Life, Liberty and Vanity Fair.

The money Geisel earned from his advertising work and magazine submissions made him wealthier than even his most successful Dartmouth classmates. The increased income allowed the Geisels to move to better quarters and to socialize in higher social circles. They became friends with the wealthy family of banker Frank A. Vanderlip. They also traveled extensively: by 1936, Geisel and his wife had visited 30 countries together. They did not have children, neither kept regular office hours, and they had ample money. Geisel also felt that traveling helped his creativity.

Geisel's success with the Flit campaign led to more advertising work, including for other Standard Oil products like Essomarine boat fuel and Essolube Motor Oil and for other companies like the Ford Motor Company, NBC Radio Network, and Holly Sugar. His first foray into books, Boners, a collection of children's sayings that he illustrated, was published by Viking Press in 1931. It topped The New York Times non-fiction bestseller list and led to a sequel, More Boners, published the same year. Encouraged by the books' sales and positive critical reception, Geisel wrote and illustrated an ABC book featuring "very strange animals" that failed to interest publishers.

In 1936, Geisel and his wife were returning from an ocean voyage to Europe when the rhythm of the ship's engines inspired the poem that became his first children's book: And to Think That I Saw It on Mulberry Street. Based on Geisel's varied accounts, the book was rejected by between 20 and 43 publishers. According to Geisel, he was walking home to burn the manuscript when a chance encounter with an old Dartmouth classmate led to its publication by Vanguard Press. Geisel wrote four more books before the US entered World War II. This included The 500 Hats of Bartholomew Cubbins in 1938, as well as The King's Stilts and The Seven Lady Godivas in 1939, all of which were in prose, atypically for him. This was followed by Horton Hatches the Egg in 1940, in which Geisel returned to the use of verse.

Geisel's most famous pen name is regularly pronounced /su?s/,^[3] an anglicized pronunciation of his German name (the standard German pronunciation is German pronunciation: ['z???s]). He himself noted that it rhymed with "voice". Alexander Laing, one of his collaborators on the Dartmouth Jack-O-Lantern, wrote of it:

You're wrong as the deuce
And you shouldn't rejoice
If you're calling him Seuss.
He pronounces it Soice (or Zoice)

Geisel switched to the anglicized pronunciation because it "evoked a figure advantageous for an author of children's books to be associated with—Mother Goose" and because most people used this pronunciation. He added the "Doctor (abbreviated Dr.)" to his pen name because his father had always wanted him to practice medicine.

For books that Geisel wrote and others illustrated, he used the pen name "Theo LeSieg", starting with I Wish That I Had Duck Feet published in 1965. "LeSieg" is "Geisel" spelled backward. Geisel also published one book under the name Rosetta Stone, 1975's Because a Little Bug Went Ka-Choo!!, a collaboration with Michael K. Frith. Frith and Geisel chose the name in honor of Geisel's second wife Audrey, whose maiden name was Stone.

Geisel's early artwork often employed the shaded texture of pencil drawings or watercolors, but in his children's books of the postwar period, he generally made use of a starker medium—pen and ink—normally using just black, white, and one or two colors. His later books, such as The Lorax, used more colors.

Geisel's style was unique—his figures are often "rounded" and somewhat droopy. This is true, for instance, of the faces of the Grinch and the Cat in the Hat. Almost all his buildings and machinery were devoid of straight lines when they were drawn, even when he was representing real objects. For example, If I Ran the Circus shows a droopy hoisting crane and a droopy steam calliope.

Geisel evidently enjoyed drawing architecturally elaborate objects, and a number of his motifs are identifiable with structures in his childhood home of Springfield, including examples such as the onion domes of its Main Street and his family's brewery. His endlessly varied but never rectilinear palaces, ramps, platforms, and free-standing stairways are among his most evocative creations. Geisel also drew complex imaginary machines, such as the Audio-Telly-O-Tally-O-Count, from Dr. Seuss's Sleep Book, or the "most peculiar machine" of Sylvester McMonkey McBean in The Sneetches. Geisel also liked drawing outlandish arrangements of feathers or fur: for example, the 500th hat of Bartholomew Cubbins, the tail of Gertrude McFuzz, and the pet for girls who like to brush and comb, in One Fish, Two Fish, Red Fish, Blue Fish.

Geisel's illustrations often convey motion vividly. He was fond of a sort of "voilà" gesture in which the hand flips outward and the fingers spread slightly backward with the thumb up. This motion is done by Ish in One Fish, Two Fish, Red Fish, Blue Fish when he creates fish (who perform the gesture with their fins), in the introduction of the various acts of If I Ran the Circus, and in the introduction of the "Little Cats" in The Cat in the Hat Comes Back. He was also fond of drawing hands with interlocked fingers, making it look as though his characters were twiddling their thumbs.

Geisel also follows the cartoon tradition of showing motion with lines, like in the sweeping lines that accompany Sneelock's final dive in If I Ran the Circus. Cartoon lines are also used to illustrate the action of the senses—sight, smell, and hearing—in The Big Brag, and lines even illustrate "thought", as in the moment when the Grinch conceives his awful plan to ruin Christmas.