Theodor Geisel transformed the way young people learn to read. On thecentenary of his birth, Eileen Battersby explains how he did it.

If one man could claim to have single-handedly taught millions of children to read, that teacher would have to be Theodor Seuss Geisel, better known to the world as Dr Seuss, author of more than 50 books. The creator of maverick superstars such as the Cat in the Hat and the Grinch, Geisel was born 100 years ago today in Springfield, Massachusetts. Book titles, children's literature and learning to read would never be the same again. Nor, come to thinkof it, would the rhyming couplet.

Generations of North American children began their adventures with words through the rhythms, rhymes and clever use of repetition that make the inspired mania of the good doctor's crazy tales so appealing, accompanied as they are by his inimitable illustrations. Dr Seuss, international institution and Pulitzer Prize winner, enjoyed painting, gardening and bow ties. He lived in an old Californian observation tower.

More inclined to shyness than deliberate secrecy, he remains a minor enigma, the sum of his subversive imagination. The main biographical source, heavy with affection, was written by friends, Judith and Neil Morgan. He had no children; his legacy is a publishing industry and an influence that extends from Sesame Street to the present.

For all the hilarity, and at times the moral point, of the stories, much of the magic is generated by the drawings. From early childhood, Geisel, "Ted", loved doodling, and through his school years these doodles became increasingly fantastic, invariably incorporating wild creatures and bizarre contraptions. He was the son of a brewer, Theodor Robert Geisel, who himself had been born into a German immigrant brewing family.

Success and relative wealth did not shield them from racial insults during the first World War, although the Geisels were sufficiently astute to openly support the US war effort. Ted Geisel and his sister, Marnie, appear not to have dwelt on their German heritage, and they emerged as fully formed US teenagers.

Prohibition hit the family business, but life continued happily enough with Geisel senior working as a park superintendent. In later life, as a famous author and the heart of what would eventually become an industry, Seuss credited his mother, Henrietta Seuss, whose name was both his middle name and pseudonym, with having given him the rhythms that shape his work. The daughter of a baker, her party piece was reciting the "pie-selling chants" with which she had once briefed customers on special offers.

Geisel, still doodling with a vengeance, moved on to Dartmouth College, in New Hampshire, where his energies centred on the college's humour magazine, Jack-o-Lantern, of which he was briefly editor in chief. The future educationalist whose books would create an early-learning library may have been more taken with the idea of learning in theory than in practice. His academic career is sketchy. On graduating from Dartmouth he claimed to have been awarded a Campbell Fellowship - a postgraduate scholarship - to Oxford University. His proud father reported this to the local newspaper. It published the news. When Geisel admitted that his application had been rejected Geisel snr funded the venture.

In 1925 Geisel set off for Oxford to study English literature. He continued doodling and met Helen Palmer, a fellow American, whom he married in 1927. She reckoned he was an artist, not an academic. On leaving Oxford without a degree, he began submitting cartoons to various publications. One was published in the Saturday Evening Post. The editor of Judge, a New York weekly, then offered Geisel a staff job. Variations of characters later to become famous in his books first emerged in these cartoons. Another job offer appeared, in the advertising department of Standard Oil.

He remained in the advertising industry, mainly with Standard Oil, for 15 years, all the while continuing with his cartoons. His first children's book, And To Think That I Saw It On Mulberry Street, was initially rejected by 27 publishers. Finally, a former Dartmouth classmate, by then working in publishing, championed the manuscript and the book was published. It was 1937. Geisel was 33.

Too old at 38 for the draft on the outbreak of the second World War, he wanted to join in the war effort and produced up to five political cartoons a week for PM magazine. He also worked with Frank Capra's Signal Corps making movies, including a "cartoon" training series. The parts of the series featuring Private Snafu, overseen by Geisel, were scripted in rhyme.

War diverted him, but other books, such as McElligot's Pool, The 500 Hats of Bartholomew Cubbins, Bartholomew And The Oobleck, Green Eggs And Ham, If I Ran the Zoo, Horton Hears A Who! and Horton Hatches The Egg, followed.

Influential writers were arguing, meanwhile, that existing children's books were boring and that many children had no interest in reading. Dr Seuss would change that. Geisel was approached to write a children's basic reading text using 220 new-reader-vocabulary words.

The Cat In The Hat appeared in 1957. It featured the cat intent on livening up "a cold, cold wet day". Aided by Thing One and Thing Two, he defies the family goldfish and leads Sally and her brother, the narrator, on a chaotic roller coaster of an afternoon that culminates in a return to normality.

Dr Seuss was now famous. More books followed. In 1967 Helen, to whom he had been married for 40 years, died. The following year, aged 64, he remarried. Honours accumulated, and he created the Lorax, a pioneering environmentalist. He won his Pulitzer Prize and continued writing books, such as his antiwar tract, The Butter Battle Book, about the Yooks and the Zooks, and working on film projects. A film version of The Cat In The Hat opens next month.

The closing lines of his final book, Oh, The Places You'll Go!, provide a fitting epitaph: "You're off to great places! Today is your day! Your mountain is waiting. So get on your way." Theodor Geisel died on September 24th, 1991, midway through his 88th year. Dr Seuss will live for ever.