Tyler Hicks/The New York Times

There was Teddy May, the colorful former superintendent of city sewers, working a mouthful of tobacco with what teeth he had left while spinning his implausible story.

And there with him was Robert Daley, the young writer, asking the questions that would give new life — and credibility — to one of the great legends of New York City.

“I says to myself them guys been drinking,” Mr. May began. “I’ll go down there,” he continued, “And prove to youse guys that there ain’t no alligators in my sewers.”

Arthur Brower/The New York Times

That conversation on a Hell’s Kitchen stoop about whether giant reptiles patrolled the city sewers was made public 50 years ago in Mr. Daley’s 1959 book “The World Beneath the City.” The account took what had been a rumor propped up by a few isolated occurrences and helped transform it into one of those cherished facts about New York that don’t have to be true to be endlessly repeated.

That’s because, as he was saying, Mr. May decided to go down to sewers himself to determine whether there was anything other than an excess of whiskey behind his inspectors’ reports of narrow escapes from alligators. That startling description of what he found, given by the man affectionately known as the King of the Sewers and recounted by a journalist, was immortalized in “The World Beneath the City”:

Alligators serenely paddling around in his sewers. The beam of his own flashlight had spotlighted alligators whose length, on the average, was about two feet. Some may have been longer. Avoiding the swift current of the trunk lines under major avenues, the beasts had wormed up the smaller pipes under less important neighborhoods, and there Teddy had found them. The colony appeared to have settled contentedly under the very streets of the busiest city in the world.

The legend of alligators in the sewers — discarded pets that have grown large in the bowels of the city, the story goes — leans heavily on a widely cited three-page section of the book. (The city and the state no longer allow alligators or their near-relatives to be kept as pets.)

Despite repeatedly being discredited by scientists who insist that neither alligators nor their near-relatives caimans could survive the pollution, the lack of light, the limited food and the cold winters, the story has been embraced elsewhere. The subterranean reptiles appear in literature (Thomas Pynchon’s “ V.”), movies (“Alligator” and “Alligator 2: The Mutation”), television (the History Channel recently asked, “What if one of the most famous and terrifying urban legends was not a legend but a frightening fact?”) and even embraced by the city’s Department of Environmental Protection. (Though the agency insists the sewers are free of alligators, it sells T-shirts emblazoned with the “house mascot.”)

These stories were backed by scattered reports, mostly very old, of alligators living in sewer systems that appeared in papers around the country, including Atlanta, Dallas and Newark. The most widely cited of these was an article in The Times on Feb. 10, 1935, headlined “Alligator Found in Uptown Sewer.”

That article described several people — led by a teenager named Salvatore Condoluci — who had caught and ultimately killed a seven- to eight-foot-long alligator they discovered beneath an open manhole on 123rd Street near the Harlem River. However, the reptile was described as sickly, lacking “the robust vigor of a healthy, well-sunned alligator,” and it was assumed that its stay in the sewers had been brief.

Meyer Berger, who wrote the About New York column for The Times, recounted in 1957 that in the mid-1930s, sewer alligators “seemed to thrive below the pavement” in “rather frightening numbers.” The column, which offered no attribution, added: “They were destroyed systematically and the threat of an alligator invasion died away.”

“These tales had a journalistic background,” said Loren Coleman, director and curator of the International Cryptozoology Museum in Portland, Me., who has researched and written about the topic for decades. “Daley’s book came along, and it was almost like independent confirmation.”

Mr. Daley said in an interview last week that he initially resisted writing “The World Beneath the City,” which chronicles the history of New York’s underground infrastructure, because he wanted to write novels. He changed his mind when the publisher offered a $1,000 advance, which was followed by $1,700 a year later. (He went on to work for The Times, where his father, Arthur, was a Pulitzer-winning sports columnist and where his daughter Suzanne is currently the national editor.)

When discussing the book with James A. Lundy, a former Queens borough president, Mr. Daley said he was told to speak with Edward P. May, known as Teddy. “Ask him about the alligators,” Mr. Lundy commanded.

So Mr. Daley sat on a stoop with Mr. May, who described his story of disbelief and discovery and detailed his efforts to rid the sewers of the alligators: poisoning some, chasing others into the fast-moving main tunnels where they were swept out to sea, and permitting his inspectors to hunt down the rest with rifles and pistols for sport.

The New York Times Studio

“He started telling me about the alligators in the sewer,” Mr. Daley remembered. “He wasn’t joking. He told me a lot of good stuff, and I accepted it as the truth.”

“He convinced me it was a true story without even trying,” he added. “He wasn’t trying to win me over or convince me — the stuff just kept coming out.”

He said he still believed that Mr. May was telling the truth, even if the numbers could have been exaggerated. “And besides,” Mr. Daley added, “it made a terrific story. How could you turn that down?”

The tale spread rapidly.

When Mr. May died in 1960, after the publication of the book, his obituary in The Times said, “Once Mr. May led a squad in cleaning the sewers of a number of live alligators that, discarded in the sewers as tiny pets, and survived and grown large.”

In his 1963 debut novel “V.,” Mr. Pynchon envisioned a city-run Alligator Patrol — as in, “Look sharp, men of the Alligator Patrol” — whose job it was to hunt the giant, sewer-dwelling alligators.

And in 1966, an 11-year-old Frank Indiviglio descended into the Bronx sewer system with a rope and a hook baited with lunch meat, looking for alligators. “I spent a summer down there searching for them,” Mr. Indiviglio said. “A couple of hours a day, I went down there and fished for them. I knew a little bit about alligators even then, so I thought it was a little iffy. But people swore they were down there.”

Mr. Indiviglio went on to spend decades as a zoologist with the Bronx Zoo and is now a writer for a pet care Web site. His expertise is reptiles, and he now shares the consensus view that conditions would make it impossible for alligators to survive in the sewers.

Natalie Behring for The New York Times

Steven Lawitts, acting commissioner of the Department of Environmental Protection, which oversees the sewers, repeated that official position last Wednesday, adding the prudent caveats. “The legend lives on, but it’s not true, to our knowledge,” he said. “We have had no alligator sightings dead or alive, except on our T-shirts.”

Still, the occasional discovery of above-ground alligators in New York — on Staten Island, in Central Park or in Queens — refreshes the story. And of course, there was that one case in 1935.

Salvatore Condoluci, the teenager who roped that alligator, is now 92.

Though he has forgotten some of the details, he still remembers hearing the thrashing in the icy water beneath the manhole, first seeing the creature’s head, and using a rope to lasso and haul it to the surface.

But Mr. Condoluci isn’t sure whether he believes that other alligators lurk below. “I don’t know,” he said. “I really don’t know.”