The term cartoon originally described an artist's preliminary sketch for a painting, fresco, or tapestry. It later came to designate the rough and unconventional sketches a comic artist produces. Today it means any drawing or painting used for amusement, editorial, or advertising purposes. A cartoon produced primarily to entertain is called a comic strip or, in single-panel form, a gag cartoon; one used to explain or illustrate a story, article, or nonfiction book, or to form part of an advertisement, is referred to as a cartoon illustration; a cartoon used to sway public opinion or dramatize the news is called an editorial (or political) cartoon.

Editorial cartoons usually appear on the editorial pages of newspapers, although in 18th- and 19th-century Europe such cartoons, called caricatures, were sold as single sheets. Today caricature has come to refer to a drawing of an individual that exaggerates personal appearance to the point of ridicule. Caricature is usually an important element in the editorial cartoon.

The first editorial cartoons in the United States appeared in the second half of the 19th century, mainly in magazines. Thomas Nast, America's first important editorial cartoonist, did most of his work for Harper's Weekly. When photoengraving made possible quick and economical reproduction of drawings and photographs, editorial cartoons began to appear regularly in daily newspapers. Now most editorial cartoons in magazines are reprinted from newspapers.

In the United States today only about 150 people make their livings as full-time editorial cartoonists. Because smaller newspapers cannot afford to hire their own editorial cartoonists, they buy editorial cartoons from feature syndicates. Many big newspapers that have their own editorial cartoonists also buy from syndicates in order to bring different points of view to their readers. These newspapers customarily put the extra cartoons on their op-ed pages (the pages opposite the editorial pages). Most syndicated editorial cartoonists are affiliated with big newspapers that run their cartoons first, before releasing them for syndication. For instance, Etta Hulme's cartoons originally appear in the Fort Worth Star-Telegram; Newspaper Enterprise Association (NEA) then distributes them to hundreds of other newspapers.

Typically, an editorial cartoonist working for a newspaper meets with the editors each day to discuss the news and the editorial positions the paper is to take. The cartoonist returns to the drawing board to execute several rough sketches, and the editorial-page editor picks one for finishing. The cartoonist may spend several hours on the final drawing to capture just the right effects, sometimes referring to photographs for detail. Cartoons are drawn larger than they are to appear in print and then reduced photographically.

Pompous or hypocritical politicians make the best subjects for editorial cartoons. "I start with the premise that there's not a good one in the bunch," says Pat Oliphant, who is not affiliated with a daily newspaper but whose work is distributed by Universal Press Syndicate. "They're all guilty until proven innocent." Tony Auth of the Philadelphia Inquirer adds that an editorial cartoonist needs a sense of outrage. "You have to be capable of reading something and saying, ‘I don't believe that!’ and then translate that into a drawing."

Editorial cartoons are, by nature, biased. They make their points through exaggeration and work best when they attack their subject, however unfair the attack may be. Cartoons of praise are not usually remembered. Cartoons occasioned by the death of a public figure (obit cartoons) are the hardest to draw effectively. The cartoonist usually says what has to be said with a wreath, an empty chair, and a bowed head. Still, even an obit cartoon can make an impact if it is drawn well enough and if it is fueled by a powerful idea. One of the most memorable is Bill Mauldin's drawing of a bowed statue of Lincoln after the assassination of President John Kennedy. One cartoonist, Jay Norwood "Ding" Darling of the Des Moines Register, drew his own obit cartoon.

Editorial cartoonists today tend to be politically liberal. A few, including Wayne Stayskal of the Tampa Tribune and Steve Benson of the Arizona Republic, are generally conservative. The late Jeff MacNelly of the Chicago Tribune, who won his first Pulitzer Prize in his early twenties, was unique in that he seemed to be as interested in amusing his readers as in influencing them.

Several editorial cartoonists have launched syndicated comic strips to give themselves yet another creative outlet. For instance, MacNelly did "Shoe"; Mike Peters of the Dayton Daily News does "Mother Goose & Grimm"; Doug Marlette of New York Newsday does "Kudzu"; and Jack Ohman of The Oregonian does "Mixed Media."

Editorial-cartoon drawing styles generally fall into one of three schools: the ashcan school, the crosshatch school, and the built-in-texture school. The ashcan school was inspired by the work of the French caricaturist Honoré Daumier and other 19th-century lithographic artists. This style evolved in newspapers around the time of World War I, when it was used mostly by liberal or radical cartoonists concerned with poverty, among other problems. Their cartoons would often include an ash can to signify a slum area, giving rise to the school's common name. Daniel Fitzpatrick (1891–1969), for many years with the St. Louis Post-Dispatch, was an early practitioner of this style; his bold, stark drawings spawned many imitators. Herblock of the Washington Post belongs to this school, as does Mauldin.

The crosshatch school, characterized by many fine crisscross lines drawn to impart roundness to figures and props, originated with Thomas Nast and Homer Davenport, who followed him. Davenport (1867–1912) worked mostly for the newspapers of William Randolph Hearst.

Many midwestern cartoonists, including John T. McCutcheon (1870–1949) of the Chicago Tribune and "Ding" Darling, also used it. The crosshatch style fell from favor for a time, but it was revived by David Levine, the caricaturist for the New York Review of Books, and his many imitators.

The built-in-texture school attracted the nation's newer editorial cartoonists, led by Pat Oliphant and Jeff MacNelly. In this style, cartoons are drawn on paper with a shading pattern that is brought out through use of a brushed-on chemical solution. Oliphant and MacNelly eventually grew tired of the school's slick look and returned to hand-drawn shading and more lively artistry.

Cartoonists often experiment with other styles and other mediums. Paul Conrad of the Los Angeles Times, who mainly works in the ashcan style, sometimes uses a scratchboard technique for his drawings. He scratches through a coating of black ink with a knife or razor blade to expose the white of the paper. The respected British cartoonist David Low achieved spectacular effects often by using nothing but strong brush strokes and areas of solid black.

To help readers recognize certain characters and better understand cartoon ideas, some editorial cartoonists include boxes, or labels, with words inside them, but the most accomplished cartoonists, in order to keep their work uncluttered, avoid labels whenever possible. They know that the simplest cartoons are often the most effective. Most editorial cartoons have captions, often simply a comment made by the cartoonist.

Cartoonists have developed a kind of visual shorthand, a set of symbols to stand for organizations and concepts. The most familiar symbols are Uncle Sam for the United States, the donkey for the Democratic party, and the elephant for the Republican party. In the 1920s, Rollin Kirby of the New York World invented "Mr. Dry," a tall, cranky man dressed in black and carrying an umbrella, to stand for Prohibition.

An editorial cartoon is essentially a figure of speech in graphic form. Often subtle, frequently obvious, it remains a vital force in American journalism, causing people to think about controversial issues and frequently helping them form opinions.