'Water Taxi, Mount Desert,' exemplifies the work of photorealist Richard Estes. An Estes retrospective opens Oct. 10 at the Smithsonian American Art Museum. Richard Estes/Marlborough Gallery, New York

We don't know for certain the identity of the woman who has come to be known as Leonardo da Vinci's "Mona Lisa." Or whether Édouard Manet bought a drink from the girl standing behind the counter in "A Bar at the Folies-Bergère."

But we do know how "Water Taxi, Mount Desert" (1999), by Richard Estes came to be—a painting that I suspect will stand the test of time.

"Who paid for that?" Mr. Estes asked Nancy Monfredo of the boat ride depicted in the work, which shows Ms. Monfredo and her daughter, Nina, seated on a wicker chair gazing out at the ocean as they headed back to Northeast Harbor, Maine.

"You and I did," Ms. Monfredo recalled, as she sat in the living room of Mr. Estes's home in Maine last week. "Twenty dollars apiece." She added, laughing: "You said, 'I'll take some pictures and I can deduct this.' "

"I had about three frames left on the film," remembered Mr. Estes, perhaps America's greatest Photorealist painter. "I wanted to use it up so I could have it processed."

Mr. Estes at his home in Northeast Harbor, Maine. Ralph Gardner/The Wall Street Journal

I visited Maine with several goals in mind: to swim and hike in Acadia National Park, to consume several lobster rolls and to see the retrospective of Mr. Estes work, "Richard Estes' Realism" at the Portland Museum of Art. The show runs through Sept. 7, then travels to the nation's capital, where it opens Oct. 10 at the Smithsonian American Art Museum.

I'd seen reproductions of "Water Taxi, Mount Desert" but never the painting itself, which normally resides at the Kemper Museum of Contemporary Art in Kansas City, Mo.

The original didn't disappoint. Like Manet's "A Bar at the Folies-Bergère" or other great portraits, its timelessness is set off by a sense of immediacy.

I don't think it makes any difference to my appreciation of the painting that Ms. Monfredo was my wife's college roommate or that we were on our way to see her and her husband, Paul, in Northeast Harbor. Nina, now 25, lives and works in Manhattan. None of the other museumgoers knew our friend. But as with a Vermeer, the image attracted a crowd.

I recall the painting that first drew me to Richard Estes's work, if not the year or even the decade. Titled "Drugs" and painted in 1970, it depicts the streamlined facade of Weiner Drugs, the word "DRUGS" in large neon letters above it. The pharmacy, long gone, stood on the southeast corner of 72nd Street and Columbus Avenue. That's where I'd spend my 25-cent allowance as a child. I had a particular weakness for Nestlé Crunch bars.

Another of his works is 'Diner.' Richard Estes/Marlborough Gallery, New York

"My parents came to visit me once," Mr. Estes remembered of the '60s and the neighborhood, less glamorous in those days. "I was living on 75th Street between Central Park West and Columbus. We were going to go out and eat. We couldn't find a restaurant on Columbus Avenue. We had to go to Broadway."

While the portrait of the Monfredo women was the main incentive to visit Portland—the food scene coming in a close second, especially for my daughters—the exhibition also made a case for Richard Estes as the most significant landscape painter of New York City.

These days, Mr. Estes divides his time between Maine and his apartment in the Eldorado on Central Park West. He paints for several hours in the afternoon.

Whether diners seated around a table at the Automat (1966-1968), Sunday afternoon sunbathers in Central Park (1989) or the Shake Shack on Columbus Avenue and 77th Street under scaffolding—the work that sat on his easel the morning I visited—Mr. Estes imbues his scenes, no matter how seemingly commonplace, with a delicacy and poignancy that rivals those of his influences, ranging from Canaletto and Frederic Church to Edward Hopper.

"Half of New York is under scaffolding," he explained.

'Brooklyn Bridge' Richard Estes/Marlborough Gallery, New York

While ours was more a social visit than a formal interview, Mr. Estes's fundamental modesty showed through—as it does in his art, where his signature is often hidden in plain sight.

He claims that several of his paintings decorate his walls, only because he can't sell them—"Art collectors are funny," he said. "They don't necessarily buy what they want; they buy what they think they should buy"—and that he finds painting New York City and the frozen landscape of Antarctica, the subject of a 2007 painting in the exhibition, equally challenging: "I usually have just as much trouble with one as the other."

But therein also lays the magic of his work. It manages to reduce to a bare minimum the obstructions that stand between the viewer and the truth of the subject matter.

Seeing a painting of New York City, circa 1970, makes me feel like I'm back in the '70s with all its trappings—the storefronts, subway ads and empty building lots, long since filled in.

"You inject your own personality," Mr. Estes said. "But if you think about it too much, it becomes phony."