Edward Hopper is among the most tantalizing and elusive painters in 20th-century American art. The more you look at his haunting Victorian houses, his bleak interiors and looming lighthouses, the more you wonder: Do these paintings reflect the artist's own feelings of loneliness and isolation? Or was loneliness just Hopper's stylistic shtick for an age of anxiety?

A rare exhibition of Hopper's watercolors at the National Museum of American Art--including some that changed the course of his career--amplifies this question. For these 56 watercolors, mostly done during summer sojourns to the New England coast between 1923 and the '40s, are from Hopper's only sustained effort to paint from nature, out-of-doors and on site. The better-known oil paintings, including such American icons as "House by the Railroad" (1925) and "Nighthawks" (1942), were actually inventions put together in Hopper's New York studio from sketches, memories and fleeting glimpses of city life snatched and stored as the artist prowled Manhattan's streets and rode its elevated trains.

The watercolors thus offer an opportunity to separate what Hopper (1882-1967) actually saw from what he created through his taut personality and pictorial inventiveness. It turns out that there's more invention than you would have thought.

We first meet Hopper here at age 41 at the sunny seaside resort of Gloucester, Mass., where he'd gone to paint during the summer of 1923. He'd already attracted some museum attention for his darkly shadowed etchings of lonely city life. And he'd sold one sailing picture 10 years earlier at the Armory Show. But he was still slaving away as a freelance illustrator that summer when he met his future wife, Josephine, also an artist, at his Gloucester lodging house. It was she who persuaded him to give the newly "in" medium of watercolor a try.

By the time they returned to Gloucester the following summer--married--Hopper's career had begun to take off, thanks in part to the Brooklyn Museum's purchase of "The Mansard Roof," a delicious watercolor that hangs at the start of this show. The following fall, Hopper took several more watercolors to Frank Rehn Gallery in New York and was immediately given a show that drew raves from critics. Better yet, all 16 works were sold. Soon Hopper was painting full time. From that day, he could never work fast enough to satisfy the demand. In 1930 his "House by the Railroad" became the first painting to enter the permanent collection of the new Museum of Modern Art. Three years later he had his first retrospective there.

"The Mansard Roof" is a wonderfully nostalgic scene of a grand old Gloucester Victorian house on a sunny summer afternoon, a stiff breeze puffing up the yellow awnings around the broad veranda. There are other fine Victorian house portraits here, the best being "Haskell's House" (1924), set high on a hill in bright Gloucester sunlight. But "The Mansard Roof" is especially memorable because it is so animated and contains the only convincing gust of wind in this entire show. Soon thereafter, Hopper burst forth with his mature style, which in effect stilled all breezes and removed all signs of movement from his watercolors. It also removed nearly all signs of human habitation by shuttering the windows and pulling down shades. The resulting mood is that of being at the beach after Labor Day, when all the summer people have left.

In subsequent watercolors painted during annual visits to Gloucester, the coast of Maine and Cape Cod (where, in 1934, the Hoppers built a house in Truro), Hopper came to favor subjects that didn't move--especially the fast-disappearing Victorian houses, with their mansard roofs and dormer windows, which were then widely scorned. He also painted simpler seaside dwellings, lighthouses and rusted fishing trawlers. But there's nary a sound implied--not even surf--unless you count the mournful wail that seems to issue forth from the ominous watercolor titled "House of the Fog Horn I," painted on the coast of Maine. Otherwise, as in his oil paintings of the time, Hopper's gaze had become so intense that it seemed to freeze his subjects in time, rendering them timeless--and silent.

His back to the sea, Hopper never painted the obvious stuff, even in a popular watering hole like Gloucester, where, as painter John Sloan put it, "there was an artist's shadow beside every cow . . . and the cows themselves are dying from eating paint rags." Widely read and deeply concerned with contemporary American life (he was an avid theater- and moviegoer), Hopper wandered into the poorer parts of town, painting the colorful houses of Portuguese and Italian immigrant fishermen who'd helped make Gloucester a thriving port--and were now the very people Congress had just passed immigration laws to keep out. He also understood the impact of the mechanized trawlers on the fishing industry when he painted their rusty decks and winches in bold and aggressive compositions.

It was Hopper's concern for the impact of industrialization upon the American landscape that explains his many scenes of railroad tracks slicing through the countryside, relegating venerable old Victorian houses to what was suddenly the wrong side of the tracks. "House by the Railroad" is but the most famous example; there are others here as well, many with intrusive telephone and electric power poles hogging center stage.

There are many such meanings buried within these images, and the great contribution of this show is that it forces you to seek them out and examine their secrets. Some turn out to be visual puns or metaphors, one of the most memorable being "Rocky Pedestal," a 1927 view of a Maine lighthouse that, through deft pictorial manipulation, takes on the monumental sculptural qualities implied by its title. Observed from below--a frequent Hopperesque compositional device--this bleak tower is elevated to the stature of heroic outpost. Which to him it was: The men who lived in these lighthouses often risked their lives to rescue sailors from the sea, and Hopper knew the stories, and many of the people as well.

Sometimes the history of a place alone moved him to make a watercolor. One is "Civil War Campground," the meaning of which would escape us all if not for the title. An offhand view of a seemingly insignificant precipice, the scene is centered by three utility poles that seem to march invasively across what we presume to be the hallowed campground below. About 7,000 Maine residents fought and died in the Union Army during the Civil War, and many set out from this place. Who would have thought, knowing only Hopper's New York paintings of urban angst, that such things would move and interest him?

Many artists and writers in the '20s were concerned with defining "the American spirit," and much of Hopper's success stemmed from the fact that his portraits of Victorian houses filled the bill, as people developed nostalgia for a form of architecture they had recently scorned. "You can put your finger on the weighted and clean edge of an Edward Hopper . . . and call it American," a New York Times critic wrote in 1926. These watercolors greatly broaden and deepen that perception.

Gradually, over the course of this show, these watercolors become more geometric and abstract, and darker, too, and overall rather repetitious. The best works from the later years come after Hopper and Jo build their small studio house in Truro and focus on the landscape there. The least interesting come, oddly enough, from trips to Santa Fe, N.M., and Mexico, both of them passionate, colorful landscapes with unbelievably seductive skies. Perhaps it was Hopper's New England Baptist sensibility (actually, he was from Nyack, N.Y.) that kept him from feeling harmonious vibrations there.

In any case, it was after a final trip to Mexico in 1946 that Hopper stopped making watercolors altogether and concentrated on his paintings. Later asked why, he said: "I think it's because the watercolors are done from nature and I don't work from nature anymore." But did he ever, really?

This first serious look in 40 years at Hopper's watercolors may frustrate some visitors who want to know more about his oil paintings and the larger context of his life in New York, where he lived when he wasn't on vacation. There is an excellent solution: The NMAA has organized a truly exceptional Web site (www.nmaa.si.edu/hopper) titled "An Edward Hopper Scrapbook," which is laid out like a real scrapbook, with photographs and clippings and reproductions that survey his life and career. A handful of his oil paintings--along with a computer terminal--have also been installed in the NMAA's lobby as an introduction to the show.

'EDWARD HOPPER: THE WATERCOLORS'

"Edward Hopper: The Watercolors" will continue at the National Museum of American Art through Jan. 3, 2000. It will then travel to the Montgomery Museum of Fine Arts in Montgomery, Ala., which co-organized the show. An illuminating, fully illustrated catalogue by NMAA curator Virginia M. Mecklenburg and Margaret Lynne Ausfeld has been published. Mecklenburg will give a gallery talk Friday at 2 p.m. Three lectures by notable Hopper scholars Brian O'Doherty, Gail Levin and Carol Troyen will take place on Nov. 7, 18 and 21, respectively. All events are free, but seating is limited. For reservations call 202-357-4511.

The NMAA is at Eighth and G streets NW, near the Gallery Place Metro station. Museum hours are 10 a.m. to 5:30 p.m. daily, closed Dec. 25. Admission is free.