How many works of art does it take to make a full exhibition? If the painter is Winslow Homer, the show could have hundreds of works. If it’s Vermeer, fewer than 40.

A new show at the Farnsworth Museum of Art features 19 watercolors by Edward Hopper, whose output was much greater. But “Edward Hopper’s Rockland,” which runs through Sept. 26, features a related group of paintings spawned during the artist’s seven-week stay there in the summer of 1926.

A handful of Hopper’s paintings are among the most recognizable in the national sensibility. Nighthawks of an all-night urban diner, scenes of Portland Head Light and the lonely mansard roofs of Gloucester are all embedded in the American imagination.

None of those works is in the Rockland show. Instead, curator Suzette McAvoy has collected a series of works that examine the timeless light, contours and icons of a working fishing port. Trawlers, hulls, railroad crossings, schooners, limestone quarries and old houses were the still-life subjects that interested Hopper that summer. He produced 20 paintings from his only visit to Rockland, and almost all of them are in this show, reunited for the first time.

While there are few signs of human life in this unique collection, there is, most significantly, a pervasive sense of Hopper’s own mobility. It’s intriguing to imagine him traveling the streets on foot, stopping at a brick building or down on the dock to put his paintbrush to work. So contained are the images that you cannot hear the harbor bells or seagulls that surely played in the background of his experience. These are vacuum-packed moments, a private view into Hopper’s own silent, psychological relationship with the objective world.

That determination infuses the narrative of his paintings. This is largely familiar territory; isolation, desolation and loneliness are here. “Haunted House” with its shaded interiors and overgrown yard draws the viewer into Hopperville, where the shadows suggest a monster frozen in a lunge of outstretched arms.

“He is one of the first artists for whom we used the term ‘sense of place,'” said McAvoy last week. “Now it’s a term we use a lot. He was one of the

first artists that defined American scenery, and he was very influential on the artists who came after him, including Andrew Wyeth.”

Hopper, who lived from 1882 to 1967, somehow isn’t as neatly figured as Wyeth, however. That sense of the prettiness that creeps into Wyeth dissipates in the headier themes of Hopper. The two have a dialogue going on, but you never wonder which has the deeper voice. It’s Hopper. (Deeper still would be Hopper’s mentor Robert Henri, who had persuaded his student to paint on Monhegan Island a decade earlier.) It is not a rollicking Rockland that Hopper saw. Rather, the town is sometimes pastoral, sometimes gritty, sometimes sleepy, often haunted. If you didn’t know better, you’d think Rockland was a ghost town, wiped out by a mysterious force.

It’s oddly comforting to witness a Maine summer documented without a stroke of sentimentality. If you knew Rockland only through Hopper’s eyes, you might ask the conductor not to bother stopping the train until you got to the Mount Desert Island of Fitz Hugh Lane and John Marin.

Likewise, if this small show, which commemorates Rockland’s sesquicentennial, were your only exposure to Hopper, you might also move on. Certainly, you would acquire only a hint of his richer tones and moods, his brighter colors and alienated figures. That’s not to say you won’t instantly recognize Hopper at work here. The big shade trees, the abandoned boats, the vacant lanes, the evacuated buildings and the architecture of desertion all point directly to his atmospheric themes and angular interests. But it leaves you a little hungry for more.

“People were not primary. It was setting and landscape that interested him in these works,” said McAvoy. “He implied people and their presence, and gave them a lot of sympathy. He was very respectful of working-class people and American history. Those were sought-out subjects, and Hopper found that here in Rockland.”

Where Hopper didn’t find his heart’s desire was Eastport. He and his wife, Jo, had originally intended to spend the summer Down East, but reportedly finding little to stimulate his work there, they took the train from Bangor to Rockland, where he completed the nearly two dozen paintings.

McAvoy pointed out “Civil War Campground,” a loosely painted landscape washed with yellows and oranges, as indicative of Hopper’s interest in American history. She could have easily been referring to “Rockland Harbor, Maine” with its industrial building of rust-red hues, or “Railroad Crossing,” for its nearly gothic sense of rural life.

The show was, in part, built around “Schooner’s Hull,” which was given to the Farnsworth last July, and increased the museum’s holdings of Hopper’s Rockland period to five. If there were a subsection to this small show, it would be called Hopper’s “fishing boats.” They don’t echo the dories from his days in Ogunquit or the tipped sailing vessels of Cape Cod. Instead they are dark, worn, resolved.

This is not a Rockland where you want to spend a vacation. It’s slightly threatening. But this is a show that makes you want more Hopper. One way to get closer to the man himself? Take a walk around Rockland, look at it anew, perhaps through the eyes of one of America’s important painters.

“Edward Hopper’s Rockland” runs through Sept. 26 at the Farnsworth Art Museum in Rockland. For information, call 596-6457 or visit www.farnsworthmuseum.org. Alicia Anstead can be reached at 990-8266 and aanstead@bangordailynews.net.