Bellows’ interest in the underside of life in New York City was epitomized by a series of paintings and drawings of street youngsters playing and schmoozing in back alleys, and in lively, realistic portraits of poor kids like “Paddy Flanagan,†1908. Painting with bravura and perception, the likeness offers insights into a scrawny but cocky youngster who appears well-suited to survive on Manhattan’s mean streets. Erving and Joyce Wolf.

Any doubts about the greatness of the art of George Bellows (1882‱925) should be laid to rest by the superb retrospective on view at the National Gallery of Art through October 8. With 130 paintings, drawings and lithographs of tenement children, boxers and the dynamic urban landscape of turn-of-the-century New York City, as well as Maine seascapes, sporting scenes, World War I polemics, family portraits and views around Woodstock, N.Y., it offers ample evidence of his changing styles, compositions, subjects †and enduring achievements.

“Arguably the most important figure in the generation of artists who negotiated the transition from the Victorian to the modern era in American culture,” according to gallery director Earl A. Powell III, Bellows was the most acclaimed artist of his generation. While documenting the artist’s youthful, meteoric rise to national prominence, curator Charles Brock also explores the largely neglected period preceding his early death, when Bellows turned restless experimentation into new directions for his art.

Bucking the conventional view that Bellows’ best work came early, before the 1913 Armory Show, in his prizefighting and gritty views of Manhattan, Brock posits that in his later work he was a precursor to Modern art in America.

George Wesley Bellows was born and raised in Columbus, Ohio, the only child of a successful builder and the daughter of a New England whaling captain. He recalled, “I arose surrounded by Methodists and Republicans.”

Bellows excelled at drawing and sports while growing up and while attending Ohio State University, where he illustrated student publications and was an outstanding basketball and baseball player. In his junior year, offered a contract by the Cincinnati Reds to become a major league baseball player, he opted instead to become a major league artist, dropping out of college and heading to New York City to study painting.

Recalling happy times a decade earlier on Monhegan, Bellows painted a reprise of an earlier sketch in “Fisherman’s Family,†1923, emphasizing the closeness of husband, wife and child amid rugged island topography. As Columbus curator Melissa Wolfe observes, “A decade of experimentation tempers the artist’s vigorous palette to convey a deeply emotive poeticism.†Private collection.

Starting in 1904, he became a star pupil of Robert Henri at the New York School of Art, adopting his mentor’s bravura, painterly, expressive style to depict the world around him. To the young Ohioan, New York was an exciting city on the move, filled with construction sites, bustling crowds and all manner of activities. He responded sympathetically to the lower classes and was intrigued with the social elite. In two decades, Bellows painted 55 views of the Big Apple.

Bellows tried to get his arms around this eclectic urban scene in such ambitious early works as a striking charcoal, “Election Night, Times Square,” overflowing with revelers and characters; “New York,” 1911, a colorful oil mingling stylish pedestrians, teamsters, a street car, a policemen and towering buildings, and “Cliff Dwellers,” a boisterous tenement scene.

The young artist was attracted to the building boom in Manhattan, especially the large, deep midtown excavation for the Pennsylvania Railroad Station. Bringing together for the first time all four Bellows paintings of the subject, the exhibition underscores the harsh, dirty task of carrying out the five-year, eight-acre project that culminated with McKim, Mead and White’s grand beaux-arts building (demolished in the late 1960s). Bellows’ raw, forcefully painted views showed the vast pit covered with grimy snow; at night; at twilight with smoke and machinery visible; and the nearly completed station enveloped in haze in the evocative “Blue Morning.”

Bellows relished scenes of Manhattan in winter, whether depicting men working the docks and dumping snow in frigid conditions, or folks at leisure strolling amid fluffy drifts or ice skating, as in “Joy of Winter.” He was also drawn to the industrial waterfronts of both the East and Hudson Rivers, fascinated by the smoke and activity of tugboats and views across the rivers in all seasons.

In one of his most beautiful †and last †paintings, Bellows depicted the structure he planned and helped build two years before, amid glorious natural surroundings, in “My House, Woodstock,†1924. “Aside from a feathery handling of paint in the sky,†says Cleveland Museum of Art curator Mark Cole, “the composition teems with direct brushwork applied in urgent daubs; its vivid color scheme, employing a wide spectrum from purple through red, approximates the brilliance of the autumnal setting.†Michael A. Mennello, Winter Park, Fla.

He gained early attention with paintings and drawings of lower-class boys skinny-dipping in the East River and street urchins playing and fighting in back alleys. By 1913 he had married fellow art student Emma Story, with whom he had two daughters, and had five paintings and numerous drawings in the Armory Show.

Bellows began to work in lithography in 1916, producing some of his finest work, often on social issues of the day. He contributed regularly to the left-wing journal The Masses, edited by his friend John Sloan. Particularly compelling is his response to capital punishment via the electric chair and to a spate of lynchings in the South in the 1920s. “The Law is Too Slow” is an exceedingly graphic drawing of a black man being burned at the stake. It was used to illustrate an NAACP anti-lynching campaign.

As a man of the left, Bellows the graphic artist devoted numerous works to the lives of the poor and destitute, race relations, social problems and religious issues. He forcefully satirized evangelists, training his sights on former major league baseball player and charismatic preacher Billy Sunday. Bellows made fun of Sunday’s athletic, histrionic poses while haranguing huge crowds, and depicted the “saved” fainting and swooning among hysterical converts in an expressive painting, “The Sawdust Trail.”

Around 1916, Bellows developed a strong interest in art theory, notably the color principles of Denman Ross and Hardesty Maratta and compositional theories of “Dynamic Symmetry” espoused by Jay Hambridge. Ever restless and ambitious to improve his work, the artist welcomed the challenge of experimenting with new concepts, new approaches. The result is an artist whose art defies categorization.

Bellows is best known for images conveying the raw passion of boxing. At a time when prizefighting was outlawed in New York and had to take place in private social clubs, a trio of his paintings, highlighted by the brutal combat of “Stag at Sharkey’s,” 1909, raised these tawdry scenes to high art. “Stag,” with its broadly painted, contorted figures locked in mortal combat and grotesque, Goya-like fans looking on, remains the greatest boxing painting of all time.

As exhibition curator Charles Brock correctly summarizes, in “New York,†1911, “Bellows strove to encompass the entire life of Manhattan within the borders of a single canvas.†Choosing as his vantage point an area roughly around Madison Square, the artist presented aspects of street life, transportation, advertising and the towering buildings of the burgeoning city in an animated and colorful image. Measuring 42 by 60 inches, it is owned by the National Gallery of Art.

Bellows’ early portraits featured resilient street urchins with attitudes, and the standout “Little Girl in White (Queenie Burnett),” 1907. In later portraits, Bellows demonstrated a talent for conveying personality in both young subjects (“Madeline Davis”) and old sitters, as exemplified by two stunning likenesses, “Mrs T in Cream Silk, No. 1” and “Mrs T in Wine Silk.” His portraits of his wife and family are palpably affectionate and intimate. Bellows depicted his handsome, serene wife Emma at the piano, posing in various dresses and in the company of her daughters.

Some of his finest paintings resulted from summers along the Maine coast, notably on Monhegan Island, off midcoast, to which he was introduced by Henri. Bellows found the island with its towering headlands, crashing waves, verdant forest and hardy fishermen a ready source of inspiration. Painting with extra gusto, he documented foaming white waves smashing against dark rocks, fishermen bending to their tasks and his family gathered in island settings.

In the early years of World War I, Bellows, ambivalent about American involvement, was neither a pacifist like Sloan nor a supporter of intervention like his colleagues William Glackens and George Luks. That changed after the Bryce Report and other accounts detailed widespread atrocities committed by the German invaders of Belgium.

Working with a convert’s frenzy, Bellows turned out in rapid fashion a number of bloody, hard-hitting paintings and lithographs illustrating horrific acts by German soldiers, including burning, looting, beatings, dismemberments, shootings and rapes of Belgian civilians.

Familiar with Francisco de Goya’s “Disasters of War” series depicting atrocities during Spain’s bloody war with France, Bellows executed similar scenes of brutalization of noncombatants by Germans. Bellows tried to create works that were both classical in style and propagandistic in message. Charles Dana Gibson, who produced illustrations supporting the war effort, wrote Bellows that “These war things of yours are tremendous. I hope they hang in the room when they discuss peace terms.”

As an athlete himself, Bellows was drawn to illicit boxing matches staged in athletic clubs where fighters and fans became “members†to witness pugilistic brawls. In the greatest boxing painting of all time, “Stag At Sharkey’s,†1909, the artist employed slashing brushstrokes, dramatic lighting and expressive color to capture not only the gladiators locked in combat, but the atmosphere of cigar smoke and body heat generated by patrons fueled by animalistic bloodlust. National Gallery of Art.

Bellows’ dark, somber and gruesome lithographs focused on German brutality and the plight of victims, often turning “specific incidents of cruelty into epics of suffering,” says art historian Carol Troyen. They showed nude civilians serving as human shields for German soldiers, drunken troops molesting Belgian women and “useless” noncombatants returning from forced labor stints. “Murder of Edith Cavell,” both a lithograph and painting, immortalized the British nurse who was executed by the Germans for aiding the escape of British prisoners.

Some lithographs were translated into monumental paintings that Bellows modeled on the work of what he called “the wise old guys of Italy and Spain,” notably El Greco. The most important war paintings †”The Germans Arrive,” “The Barricade” and “Massacre at Dinant,” all 1918 †are highly structured and overflowing with German brutality. But the idealized, static figures and classical gestures and poses tend to drain the power out of the pictures. Says Troyen, “Bellows’ emulation of the representation of suffering in past art, particularly in instances when he used a more staged, historical approach to his subjects, lessened their impact and obscured his intent.”

Dismissed by many as an aberration in Bellows’ career, his war paintings are seen by Troyen as “an ambitious yet problematic attempt to marry propaganda with the grand manner, an attempt to inspire the best in human nature while depicting it at its worst.”

In 1922, attracted by the varied landscape and presence of numerous artist friends, Bellows built a house/studio in bucolic Woodstock, N.Y. There he continued experimenting with his work, creating some of his most interesting and forward-looking canvases.

They include the somewhat surreal “The White Horse”; a vertiginous, bird’s-eye view of “The Picnic”; an affectionate portrait of his winsome, 9-year-old daughter, “Lady Jean”; a stylized but perceptive likeness of a dignified elderly country couple, “Mr and Mrs Phillip Waase”; a startling image of a naked woman and bundled up female seated side by side, “Two Women”; and the colorful, beautiful Impressionistic “My House, Woodstock.”

Summering on the midcoast Maine’s Monhegan island, Bellows paid tribute to its hardy fishermen in the brightly hued, vigorously brushed and animated “The Big Dory,†1913. The artist’s careful, complex composition, with the diagonal push of the fishermen’s figures and the boat contrasting with topographical horizontals, results in “an intricate composition masked as a simple and natural scene, a true testament to Bellows’ mastery,†says Corcoran Gallery of Art chief curator Sarah Cash. New Britain Museum of American Art.

In curator Brock’s view, these late paintings “paid homage to Titian, Hals, Rembrandt van Rijn and Renoir, as well as Eakins and American folk art. They looked forward to figurative works of the 1930s by artists such as Grant Wood, Thomas Hart Benton and, later in the century, Philip Pearlstein.” He observes that the Woodstock paintings conformed “neither to the dictates of tradition nor to those of Modernism, and were too imaginative and eccentric to be easily summarized; they continue to defy any standard critical appraisal.”

In 1925, aged 42 and at the height of his powers and knowledge, Bellows died of a ruptured appendix and peritonitis. Since then, he has tended to be regarded as an all-American painter whose reputation rested on his early work. The totality of his achievements and his movements toward avant-garde images were obscured or ignored. Recent rethinking of his oeuvre, suggesting the broader scope of his aspirations and his incipient Modernism, culminate in this thought-provoking exhibition.

In the end, Brock and his exhibition leave us with the unanswerable question: “What would this immensely talented artist have accomplished had he lived another 42 years and died in 1967, like [his exact contemporary, Edward] Hopper?”

After Washington, the exhibition travels to the Metropolitan Museum of Art (November 14⁆ebruary 18) and Royal Academy of Arts, London (March 16⁊une 9, 2013).

The exhibition catalog, loaded with illustrations and perceptive essays, is published by the National Gallery; it sells for $60, hardcover and $40, softcover.

The National Gallery is on the National Mall between 3rd and 9th Streets at Constitution Avenue NW. For information, www.nga.gov or 202-737-4215.