Art and illustration are an indissoluble marriage. All art illustrates something, if only an artist’s sense of play or pretensions to philosophy. But for simplicity, consider illustration as art created for reproduction, mainly in books, advertisements and periodicals.

“Stories To Tell: Masterworks From the Kelly Collection of American Illustration” is a captivating – and obliquely provocative – exhibition of some 90 oil paintings, watercolors, and drawings from the Golden Age of American illustration. Between 1890 and 1935, artwork commissioned for books and magazines put a distinctive stamp on the visual life of the nation, often rising to a homely poetry. It is no exaggeration to say, with curator Chris Fauver, that “the product of the artist’s studio had never been so culturally relevant.”

Illustrators of the period were artists of high talent, rigorously trained, often exceptional paint handlers. Many were touched with genius; their images were memorable and their power to persuade immense. Much of their strength came from the primacy of their relationship to the canvas. Howard Pyle, Maxfield Parrish, Dean Cornwell, Norman Rockwell, and many others were painters first.The requirements of photomechanical processes took a backseat to the perfection of their work.

What strikes you immediately is the painterliness, frequent bravura, and linear grace everywhere on view. Startling attention to texture, transitions, and transparencies appear even in details that would escape reproduction. Frank Schoonover’s darkling burial scene, for example, is beautifully executed in full color despite its destiny as a half-tone for Harper’s Monthly. Franklin Booth’s pen-and-ink drawings are a feast of subtleties best distinguished in the original. Each entry testifies to the living hand and eye of its maker, an optical enchantment our digital design software cannot replicate.

Like commissioned artists down the centuries, illustrators designed within a range of dictated parameters: specified subject matter, dimensions, format, deadlines.What they surrendered in artistic freedom (a once-expansive concept now shriveled to a fetish), they gained in mass exposure and a certain social efficacy. Their work served functions more quotidian than those mediated by gallery art. Recognizing the scope of illustration’s influence is critical to understanding American art in its entirety.

The U.S. government distributed 4 million copies of James Montgomery Flagg’s “I Want You” (1916) recruiting poster, with its still-famous image of Uncle Sam pointing straight at you. Countless more Americans saw each copy. Equally pervasive and influential was the “Gibson Girl,” Charles Dana Gibson’s icon of self-possession, which epitomized smart contemporary womanhood. Harvey Dunn created haunting images under combat conditions as a military artist during World War I.

It is the storytelling role of illustration that most endears itself. Many of us came to books through pictures.The black-and-white line drawings of “Black Beauty” made the life of a Victorian carriage horse crucial to a child in the Bronx. Before handheld video games and the ubiquity of television, books kept us company.And great illustrations helped make good readers. The sound of pages turning was the sound of a child’s own loneliness, transformed into something fertile and sustaining by stories and pictures.

Nothing could better demonstrate the change in children’s culture than Jessie Willcox Smith’s illustrations of such classics as “Little Women” and “Heidi.” A contemporary of Beatrix Potter, Smith made vivid the plainspoken decencies of the stories she portrayed. Her lovely bedtime story watercolor of a child practicing piano, “Scales” (1907), is a tender but pointed example of sobriety and concentration. (Note the use she makes of Mary Cassatt in a 1902 cover for Scribner’s Magazine and the iridescent veils of wash in “Watering the Hollyhocks.”)

Howard Pyle, called “the father of modern illustration,” championed illustration as a distinctly American art form. His students, known collectively as the “Brandywine School,” became the next generation of great illustrators. His gifts for color, composition, and dramatic narrative go unrivaled. Pen drawings lead the audience to Lucas Van Leyden and German Renaissance prints. His Robin Hood, medieval knights, swashbuckling pirates, and colonial revolutionaries kept more boys at their books than today’s educa tionists seem able to do.

N.C. Wyeth, Pyle’s best-known student, flourished on the tension between the confines of delineation and Impressionism’s broken color. His work for Scribner’s series of illustrated classics was magnificent. Characteristic massing of shadowed forms in the foreground against brilliant backlighting, so marvelous to look at, is epitomized here in his cover for “The Boy’s King Arthur” (1917). Wyeth’s images fired readers with the excitement of history and myth. A handful of illustrations established a pictorial melody that young imaginations could carry through the text. No headphones needed.

J.C. Leyendecker created more than 300 delicious Saturday Evening Post covers, second only to Norman Rockwell. In a day when men wore hats even to Yankee Stadium, what would they have done without the stylish, playful, sometimes sly aplomb of Leyendecker’s Arrow Collar Man? Compare his ads with contemporary Calvin Klein spots, and you confront the significance of our visual commercial environment and its impact on communal sensibilities.

As Richard Rorty put it in another context, “Socialization goes all the way down.” Right down to what we see on billboards. This sympathetic exhibition suggests democratic culture has more at stake in the character of advertising than in so-called fine art. The popular soul does not depend on ever-expanding museums or gallery goods; it lives in intricate dialogue with mass-produced images.

It is chastening to find confidence in the validity of aesthetic intention so keenly at play in “mere” illustrations. Perhaps the charge of naivete, dismissively thrown at illustrators of this era, is better directed at inflated claims for fine art.

Until May 21 (580 Madison Avenue, 212-759-0606).