He soon convinced his mother to allow him to go to Chicago, where he unsuccessfully sought a position as staff cartoonist with a newspaper. He enrolled in night classes at the Holme School of Illustration while working in a local architect office. In 1901, Knott left Chicago to accept a position as an illustrator at a Dallas engraving shop. Four years later, in 1905, Knott accepted a full-time job at The Dallas Morning News doing illustrations. After spending three semesters (1910-1911) studying art in Munich, Germany, at the Royal Academy of Art, Knott returned to the Dallas News, where his improved skills earned him the job of editorial cartoonist, not to mention the front page.
As editorial cartoonist for The Dallas Morning News, John Knott drew five to six cartoons a week until Jack "Herc" Ficklen joined the paper in 1946 as an editorial cartoonist. Knott's timeless war cartoons attracted national and international attention for their powerful graphic quality and insightfulness. When he was awarded an honorary doctorate degree from Baylor University in 1920, then President Samuel P. Brooks said to Knott, "No single man in Texas did more towards winning the war than the high and lofty cartoons you drew."
His single most famous character, "Old Man Texas", was created in 1906 and became the symbol of the state of Texas. Based on a Lancaster, Texas, farmer, Knott used the handle-bar mustached character hundreds of times in his cartoons.
Knott is often set apart from other editorial cartoonists because of the artistic quality of his work. As opposed to characters that were overtly "cartoon" in form, Knott depicted very realistic figures. Cartoonist Bill McClanahan said he was "more of an artist than a cartoonist."
Knott received many awards throughout his career, including an honorable mention for the Pulitzer Prize in 1936. His work has been reprinted in the Wall Street Journal, the New York Evening Post, the New York Herald Tribune and the Los Angeles Times.
An exceptionally shy man, Knott retired from the News in 1957, with more than 15,000 cartoons and over 50 years of work at the newspaper.