Still, she wasn’t surprised that her son had turned it into a protected artists’ retreat. “He’s been full of adventure since he was little,” she said.

Growing up in suburban Detroit, Mr. Gorski said, he hated the way the land was “cut up and divided,” and preferred wilderness areas where he could hike and camp. “There was a point where I said, I can be a fishing guide or a park ranger for the rest of my life,” he recalled.

But now, he said, he is happy living in the city and views Rabbit Island as an escape (he often goes alone in the off-season) and a platform for his ideas about land conservation and thoughtful development. Basically, he has created a miniature national park and made himself its steward.

He couldn’t have found more virgin territory: aside from the remnants of a late 19th-century fishing shack, and ashes from the locals who have long come here to cook out and swim, the island bears no sign of human habitation. Even the previous owners, a wealthy couple from Utica, Mich., who invested in land in the Upper Peninsula, never set foot on the island.

Mr. Gorski has tried to keep development minimal and considered. This summer he has been building a second lean-to 100 or so yards from the main camp, which he plans to equip with a traditional Finnish sauna. But it was “a big compromise that we imported lumber” by boat, he fretted, rather than felling native trees.

Mr. Ranville, as Mr. Gorski is quick to point out, has been instrumental in all of this. Shortly after Mr. Gorski bought the island, the two men got to talking and decided to create a retreat for artists, using a Kickstarter campaign. Mr. Ranville, who lives in London, has spent a number of two-month stretches here over the last few years, clearing paths, documenting the island’s wildlife and working on his art.

But for all the efforts to make the island a Walden-like escape, modern realities have a way of intruding. Among the visiting artists, Brooklyn was heavily represented demographically; Portland, Ore., was a close second. There was so much Patagonia clothing on display, the campsite looked like a catalog shoot. And the focus seemed to be as much on the battery life and reception of Apple devices as on creative projects. At one point, Ms. Lee grew frustrated trying to upload a photo of a double rainbow to Instagram. Mr. Drennen, the musician from Oklahoma City who had established himself as the group’s joker, shook his head mock-ruefully and said, smirking, “So many gramable moments.”