There aren't all that many candidates for favorite American painter. Winslow Homer? Norman Rockwell? Andrew Wyeth? Factor in artistic achievement, and none of them -- not even Homer -- quite rivals Edward Hopper. Note the size of the crowds at the Museum of Fine Arts for the large Hopper retrospective that runs through Aug. 19. A great American artist, Hopper may be as close as we have to the Great American Artist.

Hopper's figures sit in unmistakably American space, as in "Automat." (Michael Tropea/courtesy of MFA)

The sources of his popular appeal are obvious enough: immediate accessibility; a subtle yet vivid color sense; familiar, but not too familiar, subject matter; a fondness for picturesque settings, like New York, Maine, Cape Cod; even a whiff of prurience (not until Hugh Hefner would the American female bosom be so celebrated).

Yet there's another aspect to Hopper's art that would seem to undercut his popularity. It's the quality that's most unmistakably "Hopperesque" in his paintings, equally apparent in "Nighthawks" and "New York Movie" and "Early Sunday Morning," all his best-known, best-loved work. Call it loneliness.

That loneliness is both what's most and least American about Hopper. It's least so because loneliness is not exactly a selling word. In a society that proclaims all men are created equal, the individual's apartness indicts that society. "America is a vast conspiracy to make you happy," John Updike once wrote. Loneliness foils the conspiracy.

Of course, a nation that prides itself on rugged individualism has to keep a place of honor for solitude. So we have Natty Bumppo striding through primeval forests, Ahab brandishing his harpoon, John Wayne walking out that door at the end of "The Searchers." Theirs is the Promethean apartness of outsize loners.

What Hopper reflects is something quite different, the unheroic loneliness of everyday people, people like you and me: ushers, secretaries, apartment dwellers. The Hemingway hero, another paragon of American individualism, is in control of his apartness. Hopper's people are not. It's imposed on them by the circumstances of life. Their plight reminds us that individualism without ruggedness simply means being alone -- alone even when, as in Hopper's "Room in New York," someone else is there.

"E pluribus unum," one out of many, bespeaks a citizenry coming together, uniting into something larger. What haunts the American imagination is the possibility of one lost among many, the individual trapped in his or her own solitude. American society, Alexis de Tocqueville wrote in Democracy in America, "throws [the individual] back forever upon himself alone and threatens in the end to confine him entirely within the solitude of his own heart." What's most American about Hopper is his bearing witness to that threat.

Confinement can take many forms. Hopper may have no peer in depicting American loneliness, but he was not himself alone in doing so. Walker Evans's surreptitiously taken photographs of New York subway riders in the '30s are Hopper's people seen in (literal) black and white. Willy Loman could have wandered into Death of a Salesman from a Hopper canvas. Some of the most arresting photographs in Robert Frank's "The Americans" share not only Hopper's sense of melancholy but the way space can enclose rather than liberate.

Film noir swarms with Hopper figures -- not the names above the title (whose moody apartness is exalted), but much farther down in the credits -- like so many little tears in the fabric of society. Think of Elisha Cook Jr.'s Wilmer, in "The Maltese Falcon," or Jonesie in "The Big Sleep." Or Thelma Ritter, eking out a purgatorial existence peddling neckties and shrugging at the prospect of her own murder in "Pickup on South Street."

Hopper's closest artistic counterpart isn't visual but verbal: the lyrics of Lorenz Hart . Hart's songs are marvels of dazzling, intricate wit -- except for the ones that express a bleakness otherwise anathema to Tin Pan Alley. Only their voicelessness keeps Hopper's people (the women especially) from breaking into "A Ship Without a Sail" or "Ten Cents a Dance." "I work at the Palace ballroom," Hart's taxi dancer sings, "but gee that palace is cheap/ When I get back to my chilly hall room, I'm much too tired to sleep."

Neither of those songs is a showstopper. That, too, is in keeping with Hopper. What's most terrifying about the apartness of his people is its matter-of-factness. There's nothing symbolic or allegorical about their isolation. It's simply there, like the dirt that gets under your fingernails, the shadows that sunlight casts. "All I wanted to do was paint sunlight on the side of a house," Hopper once said. There are no shadows quite like Hopper shadows: as solid, as accusatory.

The anomalousness of his 1921 etching "Night Shadows," which is in the MFA show, is instructive. A man, seen from an angle high above, walks down a wide sidewalk, alone but for his trailing shadow. A canopied building looms over him. The figure is puny, dwarfed by his surroundings. Neither heroic nor realistic, he is instead Everyman, lost in the looming city. Formally, the etching has considerable interest (the way Hopper uses the sweep of hatchings, for example, to heighten a sense of anxiety). Emotionally and thematically, it verges on bathos.

There's nothing bathetic in classic Hopper. There he maintains a balance between individual and setting, a balance that helps account for the sense of unemphatic desperation. Always, he locates his people in space (an unmistakably American space -- another bond with Frank's photographs). His people are, in fact, defined less by their personal characteristics -- a great portraitist Hopper was not -- than by their location: not who they are but where they are.

Regardless of whether it's a Maine lighthouse or a New York sidewalk, the "where" Hopper paints is almost always barely populated. His friend, the artist Guy Pene du Bois, described Hopper's New York as "a noiseless architectural world." Rather than teem and roar, his city seems on the verge of evacuation. There's the empty sidewalk of "Drug Store," the solitary customer in "Automat," the nearly deserted theater of "New York Movie."

Even in the country, where one might expect solitude to feel natural, it can seem oppressive. The man by himself alongside the gasoline pumps in "Gas" appears unsettlingly out of place (he's wearing a tie and vest, so he can't be an attendant -- yet neither does he have a car). The nocturnal lighting in "Rooms for Tourists" is far more spectral than hospitable.

The moodiness of that lighting is unusual for Hopper. He generally prefers strong, clean illumination -- ocean light, incandescent light -- without veiling. What's striking about this is that Hopper's paintings have a quality of stillness that's inseparable from the sense of solitude they convey. The great painters of stillness -- Vermeer, Chardin -- are so unlike Hopper in the softness of their light and the sense they communicate of their subjects' somehow being outside of time. The people in Vermeer and Chardin are suspended in light, as in a fine amber. Hopper's are pinned against it. Nor is there anything timeless about Hopper's figures; time imprisons them. So much of their sadness has to do with that imprisonment. "I Didn't Know What Time It Was," another Lorenz Hart lyric, could be their dirge, their anthem.

That special Hopper solitariness has never quite left us. The Beach Boys' "In My Room" is Hopper with three-part harmony turned inside out. We get the subject's perspective and hear how isolation can be solace as well as confinement. (Don't laugh at pairing the Beach Boys and Hopper. Cape light is very much akin to California light, and Hopper traveled extensively in the West in his later years. Mightn't the dejection of the usherette in "New York Movie," with her long figure and flowing blond hair, arise from her being a California girl in the wrong place at the wrong time?)

In Eric Fischl's paintings, Hopper's people have moved to the suburbs and shed their sexual inhibitions. Neither the natural nor artificial light in Philip-Lorca diCorcia's photograph "Hartford" -- it's in diCorcia's show currently at the Institute of Contemporary Art -- is anything like Hopper's, but that man looking off into space could step into a Hopper canvas and fit right in. Or just look down any crowded sidewalk -- all those people listening to their iPods, talking on their cellphones, isolating themselves from everyone around them -- it's Hopper on parade.

Ultimately, Hopper took his concern with human isolation to its logical conclusion. The last work in the MFA show chronologically is "Sun in an Empty Room, " from 1963. Ostensibly, it's a study in light, volume, and form. The light that seems to emerge from beneath the canvas's narrow palette of buff and dark goldenrod makes the painting seem closer to a Mark Rothko than "Nighthawks " or "New York Movie." Yet in this verging on abstraction a kind of emotional summing up is being offered, too. The sunny room, a place meant for human habitation, is empty not just of objects but also people.