Author Peter P. Blanchard III fell in love with Maine over the years, starting in 1972 when he did an Outward Bound course that took him to different islands every night.

“It was a little bit like being a 17th century explorer,” Blanchard said recently, sitting in the lounge at Bangor International Airport while waiting for a flight home to New York City. “You were not told by the instructors where you were; you just had to get yourself out of all these predicaments. And there was this incredible landscape unfolding as the fog lifted.”

Art and Nan Kellam, who fell in love with Maine more than six decades ago when they moved to the solitude of Placentia Island in the Blue Hill Bay, may have appreciated the “incredible landscape” around them. But it probably wasn’t what they loved about their island.

The Kellams likely loved the fog for what it brought when it enclosed Placentia Island. When ocean conditions were too rough, it meant no lobstermen or other seafarers would drop in unexpectedly. They could be completely alone.

From the Kellams’ meeting each other in Madison, Wis., to their search for an island and discovery of Placentia, Blanchard documents in his new book, “We Were An Island,” the story of a couple who chose a nearly solitary life on a Maine island.

Blanchard came to know Nan Kellam in the late 1980s, by which time Art Kellam had died and she had moved off Placentia and into a nursing home in Bar Harbor. Acting as a volunteer steward for two islands, including Placentia, for the Maine chapter of The Nature Conservancy, Blanchard and others occasionally would take Nan Kellam for visits to the island.

Blanchard drew on Nan Kellam’s journals, which she left to the Southwest Harbor Public Library in her will. Kellam gave her permission for him and artist Ellen Church to look at the journals, Blanchard said. When Church decided to focus on art, Blanchard decided to forge ahead with a writing project about the Kellams.

Source material also came from the Kellams’ so-called Big Book, which Blanchard described as a collection of private correspondence and archived materials to which both Kellams contributed.

“[The Big Book] was an eloquent statement of where they were and what they were doing, particularly of their first year,” Blanchard said. “They had a conscious idea of getting out their story eventually, but they were never able.”

“We Were An Island” includes archival photographs of the Kellams and recent photographs of Placentia Island shot by David Graham.

Art and Nan Kellam, who wed in 1935, were living in Tujunga, Calif., while Art Kellam was working as an engineer at the Lockheed Corp. As early as 1941, Blanchard wrote, the couple was thinking about a change in lifestyle in part because of the pressures of modern living. They hit upon the idea of living on an island.

After first considering the Pacific Northwest, the Kellams pursued Maine real estate. They first looked in June 1948 at the 522-acre Placentia Island, located between Swans Island and Bass Harbor, and having found their new home, returned a year later for good.

Blanchard writes of the Kellams’ first night on the island, spent in sleeping bags under an evergreen tree; the construction of a residence, which they eventually called Homewood; the Kellams’ interest in previous inhabitants of Placentia; and how they managed to fetch supplies, rowing back and forth to Bass Harbor in a small, gray dory.

The most affecting themes of “We Were An Island” come, however, when Blanchard addresses the Kellams’ relationship with outsiders — and their relationship with each other.

The couple had a few regular visitors to Placentia, but those who happened upon the island were viewed as an intrusion.

“You have this local population and then the summer visitors, and it’s an interesting intersection particularly given its location off Mount Desert Island,” Blanchard said. “There’s this question of a drawbridge. If you try to pull up the drawbridge in your life and define your setting and be overlord of your domain, as they became, you have to realize that on an island there’s going to be visitation whether welcome or unwelcome.”

Those moments Blanchard had savored about Maine, when the fog lifted and he had an eyeful of the Maine landscape during his adventure in the 1970s, had a different meaning for the Kellams. Nice days meant the possibility of boaters coming ashore or hikers looking for a trail.

Stormy days meant the couple could be closed off from the world.

“There were times, totally joyful and magical, when they were isolated because of heavy fog, a storm, high winds,” Blanchard said. “Reading their journals it’s almost childlike, a sense of, ‘we’re finally really totally separated, maybe for days, and we don’t have to go rowing to Bass Harbor because it’s too rough so we’re just going to enjoy the day.’ They did have that total seclusion.”

The reclusive nature of the Kellams’ life led to suspicions from the other side. Locals, Blanchard wrote, wondered if Art Kellam was a German spy, or had worked on the Manhattan Project and moved to Maine to escape guilt from the nuclear bombings of Japan.

None of that was true, Blanchard said. Art Kellam was part of the World War II military industrial complex, but his expertise was in designing fighter jets.

It’s just funny how if somebody does something quirky and idiosyncratic, folks sort of try to make sense of them,” Blanchard said. “It’s very easy for legends and rumors to swirl around them.”

The Kellams’ home on Placentia was destroyed in 2008 — Blanchard said it was falling down, and The Nature Conservancy doesn’t consider the conservation of structures to be part of its mission — but last he knew, their dory was still there as a reminder of the couple who lived out their dream of being entirely alone.

Even Blanchard dreams a little about doing what the Kellams did.

“I give my wife a little note every once in a while that says, ‘Year-round in Maine?’” Blanchard said with a laugh. “She hasn’t bought into it yet.”