“I hate to sell it. I don’t want to sell it, I just don’t, but there it is,” Cherie Doughan said. She and her mother, Jacqueline, live in Placida, Fla., and her sister is in Houston, so they do not spend much time in Montauk anymore. The proceeds will help pay for their mother’s stay at an assisted living home.

The family has been in the park since it looked like one. Tents first started popping up in the 1940s, and then trailers — the Doughans’ among them — and even five cabooses from the Long Island Rail Road. In 1972, a group of regulars bought the 20 acres overlooking the surfing and fishing hole of Ditch Plains and divided them into 199 parcels.

Image The look of Montauk Shores owes much to Alpha Doughan, center, shown at a Fourth of July party in 1985. Credit... Collection of Cherie Doughan

The look of Montauk Shores owes much to Mr. Doughan, who had a contract with the Liberty mobile home company, and wound up selling its $5,000 trailers to many of his neighbors to put on their $10,000 plots.

“He was kind of the mayor around here,” said Chris Shelby, a construction worker who came to Montauk Shores with his parents and then raised his children here. He recalled that Mr. Doughan collected half-finished kegs of beer and bringing them down to the beach for everyone to enjoy.

And they all rave about the giant tuna he caught — 300 pounds in some accounts, 400 in others — that fed the entire park for days.