Missouri Honors Its Own Thomas Hart Benton. Kansas City's traveling exhibition pulls together its native son's best works, again raising the question: Was he a small-timer - or a grass-roots genius?

INSIDE the main entrance of the Nelson-Atkins Museum of Art here in Kansas City, Mo., hangs a blue banner proclaiming: ``Thomas Hart Benton: An American Original.'' Eighty eight images appear in the adjoining main galleries. Some of them are huge murals 24 feet long; others, small portraits measuring only 2 feet square. They writhe and undulate with the characteristic Benton brushstroke and form. They glow with the familiar palette of electric blues, vibrant oranges, and powder yellows. There are sprawling tableaux, like the enormous mural entitled ``Achelous and Hercules,'' a mythological subject translated into the vernacular of the Missouri Ozarks. By contrast, in another room, are quiet portraits like ``Aaron,'' a painting of an 82-year-old black man born into slavery; and ``The Oboe PLayer,'' a painterly ``adagio'' of an elderly gentleman gently lifting his instrument out of its faded carrying case.

Elsewhere are dozens of other subjects - vistas of life in the cotton fields, on the levees, and in the Ozark hoedowns. Locomotives huff, steamboats toot, and Missouri fiddlers play their scratchy tunes.

And there, invisible in the air around them, you can still sense the controversies that once greeted images like the nude ``Persephone,'' once banned from some galleries and finally displayed by showman Billy Rose in a New York saloon; and ``Preparing the Bill,'' a typically astringent satire on country town ``politicking.''

``Thomas Hart Benton: An American Original,'' the first national touring exhibition to originate from the Nelson-Atkins Museum, opened to the public on April 16, one day after the 100th anniversary of Benton's birth. Benton, who died in 1975, was a confirmed Missourian. He was born in the small courthouse of Neosho, Mo., and since 1935 made his home in Kansas City.

Despite - or because of - the enormous popularity of his work, the art establishment is still sharply divided about the artistic legitimacy of the Benton legacy. Since the exhibition opened, most of the local newspapers and magazines have presented the time-worn arguments. The art critic of the Kansas City Star, for example, deplored the mannered and artificial style, calling it quirky and cranky (echoing the sentiments of critic Hilton Kramer of the New Criterion, who has called Benton a ``failed artist''). You can sense among the elder statesmen of the Kansas City Art Institute some of the rancor left over from the dispute in 1941 that got Benton fired from that institution after voicing his dissatisfactions with museums and other custodians of art.

For others, however, Benton's notorious outspokenness and plainness of subject and style permanently enshrine his position among the so-called American ``Regionalists'' of the first half of the 20th century.

Henry Adams, the curator of American art, who organized the Centennial Exhibition and wrote the newest biography of Benton (due from Alfred A. Knopf in October), is quick to jump into the fray.

``Benton was fascinated by the changes America was going through in the 1930s,'' he said in an interview for the Monitor. ``It remained one of his most consistent subjects. I think he was interested in the different regions of the United States and the contrasts between the rich and the poor. Also, he saw the important changes in technology between a farming, agricultural America and a modern, industrialized America. Those kinds of contrasts are in most of his paintings.''

Mr. Adams had been through an exhausting week of museum meetings, media promotions, and gallery previews. His office was cluttered with proofs from the Benton book, color transparencies from the more than 300 illustrations, and many original Benton sketches on the walls around us.

Nobody would have relished this new flare-up of controversy over his life and work more than Benton himself, Adams insisted, loosening his tie as if to capture the spirit of his subject. ``Benton was full of contradictions. He was born into them.''

Benton was the scion of an important political family. But the boy wanted nothing to do with politics and, in a later mural for the Missouri State Capitol, ferociously skewered the corruption that was bred in the political history of the state.

Although he came from a relatively sophisticated background, Benton went on to feign a certain ``countrified'' air. He was trained in the Paris avant-garde movements in painting during the years just before World War I - some examples of which are an important part of this exhibition. He nonetheless ultimately rejected the abstract painting pioneered by his most famous pupil while at the Kansas City Art Institute, Jackson Pollock.

``Diseased and sickly inversions'' is how he once termed the art movements of the day, and he began a famous series of murals and paintings of American history and American rural life.

Critics lumped him into a newly dubbed category called ``Regionalism,'' along with the Iowa artist Grant Wood and the Kansas artist John Steuart Curry. Benton's self-portrait appeared on the Christmas Eve issue of the 1934 Time magazine, proclaiming this new grass-roots, naturalistic approach to Americana.

``That cover made him the most famous artist in America,'' Adams avers, ``and we're fortunate to have it for the exhibition here.''

That portrait is the image of the rugged, irascible individualist that Benton was to cultivate the rest of his life. In 1935 he left New York after some highly publicized parting shots - snarls is perhaps a better word - at the art establishment and returned to Kansas City.

Between his teaching stints at the Art Institute, he managed to continue a tradition he had begun while living in New York - devoting his summer months to rambling around the backroads of rural America, harmonica in one hand and battered sketch pad and chalk in another.

He not only sketched musical subjects but learned to play on his harmonica the songs he heard. Some of the paintings in the exhibition reveal this important part of his developing sensibility.

Adams thinks this is surely one of Benton's most important contributions to his body of work. ``I think there was a side to Benton that you could call a `folkorist.' He was apt to preserve parts of American culture before they disappeared....

``I am always surprised by the many sides of this man,'' Adams continues. ``You could just look at him - he was only 5 feet, 2 inches tall - and wonder where he got his incredible energy. Even to his last days he would paint from five in the morning until the twilight.

``I think when you understand his short stature you learn something about his feistiness and you begin to respect a lot more those gigantic mural paintings.''

It seems ironic that a museum will bring his work to new audiences in Kansas City through June, then to Detroit, New York City, and Los Angeles the rest of the year. He spent much of his life lambasting the ``museum crowd,'' and now it is through their efforts that his work sees a new light of day.

``I think he wanted to get art out to the people,'' says Adams. ``He wanted to prevent it from being so precious and esoteric and so mystifying to the average human being. For him, art was something that was basic to human life - that's all. It was something that should be available and understood and enjoyed on any basis it could.''