For Jon and Michael, visiting Fire Island was “love at first sight.” On paper, the island doesn’t seem like much: a wisp of land, less than nine miles square, off the coast of Long Island. But one trip to this barrier island and you’ll find that it’s not your typical beach escape. For starters, no cars are allowed; you have to take a ferry to get there, and the “roads” are well-worn wooden boardwalks. All of that certainly wooed Jon—founder of cabin rental company postcardcabins—and Michael, but it was the history of the place that stole their hearts. The town of Cherry Grove, where the couple recently built this home, along with the neighboring Fire Island Pines, is deeply and wholly queer—and it has been since the 1940s. After a few years of weekend trips, the couple began casually looking at properties. After a few disappointing open houses, Jon and Michael were ready to give up. But then they saw one more ad for a 50-by-120-foot lot with pilings from a house that was started, and a...