If it hadn't been for a steamy romance, Joseph Stella (1877-1946) might have lived and died an unsung American artist. Old-fashioned, sentimental, drawn to pictorial cliches, the Italian-born painter had great talent in his twenties but not much vision.

Then around 1914, his inhibitions lifted by a 1911-12 trip to modernist Paris, Stella fell madly in love. Embraced by shadowy girders during midnight trysts, he thrilled to the rhythms of his grand passion -- the Brooklyn Bridge.

"To realize this towering imperative vision in all its integral possibilities," he told his friend Charmion von Wiegand, "I lived days of anxiety, torture, and delight alike, trembling all over with emotion ... in the midst of the bridge vibrating at the continuous passage of the trains."

In this rhapsodical state, Stella made his best paintings -- futurist odes to the soaring geometry of the bridge. More than any other works from the period, they express the strange fusion of spiritual yearning with modern engineering that gave the opening decades of the American century their special character. For many, Stella's Brooklyn Bridge paintings also symbolize the exuberance and vitality of New York City.

But there was a lifetime of work before and after Stella's passionate affair with the bridge that remains relatively obscure. "Visual Poetry: The Drawings of Joseph Stella," curated by Joann Moser, graphic arts curator at the National Museum of American Art, aims at partially lifting this veil. Accompanying the approximately 60 watercolors, gouaches, drawings, pastels and collages on view at the museum is a substantial catalogue in which Moser discusses in great detail the many aspects of Stella's imagery.

Alas, one comes away from the show feeling that the obscurity of the work here is, for the most part, deserved. Carried away by his own exalted emotions, the artist frequently forgot to get in touch with his subjects. There are too many images that don't ring true. For example, the silver point portraits of old men and young women are wonderfully skilled but lack character and meaning. You remember the technique but not the sitter.

A happy exception is "Immigrant Girl -- Ellis Island" belonging to the Hirshhorn Museum. Seemingly sketched on the spot (the girl's left arm is portrayed in two sequential positions), this charcoal drawing movingly straddles art and life. With her abundant, dark wavy hair and pensive profile, the girl has a classic beauty, but you can also see in her features the tired, ground-down working woman she will become.

Stella seems to have been almost as excited by the unfolding structures of flowers and plants as he was by the engineering of the Brooklyn Bridge. His flower studies are among his most delicate creations, especially when he follows the erratic promptings of nature rather than his own grand designs. But in too many of his colorful flower studies the religious symbolism gets heavy, or worse yet, cute.

The most memorable works on view are undoubtedly those inspired by the industrial might of the United States, particularly his studies of Pittsburgh. Stella first visited the steel town in 1908 to do drawings for a sociological study of workers and working conditions that was to appear in Survey magazine. The artist was overwhelmed by the "black, mysterious mass" of the city that he called "the stunning realization of some of the most stirring infernal regions sung by Dante."

Stella's portraits of Pittsburgh's workers are predictably trite. But the atmosphere of the city "throbbing with black smoke" fired his visual imagination, and he made some fine, if alarming, studies of smoking chimneys. Clearly we've come a long way in fighting pollution.

His most interesting Pittsburgh drawings were done a decade later, circa 1818-1820, during his Brooklyn Bridge period. This time, he let his eye do the talking. Sharply observed, the dark masses of "Coal Pile" and "Grain Elevator" look so starkly modern, they might easily pass for the iconic forms of Donald Sultan or Robert Moskowitz. And perhaps that tells us a good deal about the unbridled romanticism that underlies these two contemporary American painters.

Stella saw everything magnified, transfigured, resonant and larger than life whether it was a flower or a factory. When he was looking at phenomena that had no art history, his imagination and natural gifts triumphed. His weaknesses were his uncritical love of past art and a fatal inability to distinguish between genuine poetry and kitsch.

Stella's work is decidedly uneven. But the show has the additional handicap of a miserable installation. Crowded into the ground-floor corridor that ill serves the museum as a prints-and-drawings gallery, it has the tacky look of an end-of-semester exhibition. The high school impression is completed by deadly yellow panels on which the works are jammed. At his best, Stella has a tremulous delicacy of line and color that is completely overwhelmed by this brutal treatment.

On the day I visited the exhibition, the artist's droll, 1940s profile self-portrait hid behind a potted palm. I thought he looked embarrassed.

Visual Poetry: The Drawings of Joseph Stella continues through Nov. 12.