Nicholas Roberts for The New York Times

Peter Kaplan, the editor of The New York Observer, announced his resignation on Wednesday and said he would be leaving the weekly in June. For the past 15 years, Mr. Kaplan has used tart headlines and a broad mix of news articles to create a kind of contemporary municipal history of New York demimondes high and sometimes low. The newspaper let those in the know know what else they should know about.

Mr. Kaplan met with his staff at 2 p.m. to inform them of his departure, saying that after almost 800 issues, it was time for someone else to perform what some of those who work at the small paper have called a kind of a weekly miracle.

“I have been here 15 years,” he said in an interview, pointing out that his third five-year contract is up in June. “I’m 55, interested in a third act, and I’ve had my turn here. I want to take what I have learned and see if there is a way I can help figure out what is next for our business.”

Mr. Kaplan will leave a New York media world that is fundamentally different than the one he entered in 1994. Just last week, the Observer broke a story about a Brooklyn con woman, the so-called “hipster-grifter,” in a news article that provided just the kind of New York intrigue and context that had been a hallmark of the newspaper. But Gawker, the Manhattan gossip blog, immediately took custody of the story, annotating it with attitude and reader-submitted sightings of the protagonist that all but obscured where the story came from in the first place.

“We are a newspaper in a time that is fundamentally uncongenial to newspapers and we are about the reporting at a time when the economics of reporting are very difficult to justify,” Mr. Kaplan said. “There may be some similarities in tone, but we are the diametric opposite of Gawker. We don’t borrow information, we create it.”

Known for his soaring soliloquies about the city he loved but did not live in — he resides in Westchester — Mr. Kaplan is a modern version of the fedora-wearing newsman, a man who saw his paper as a weekly libretto rendered in glitz and noir. Under his tenure, the newspaper played large for its size, catching then-presidential candidate Sen. Joseph Biden taking the measure of then-candidate Barack Obama by saying he was “articulate and bright and clean”; getting an interview with Jayson Blair at a time when his reporting for The New York Times was coming apart, and all but creating a television and movie franchise with its “Sex and the City” column.

Mr. Kaplan’s skepticism and unalloyed enthusiasm has left a footprint on the vocabulary of contemporary journalism. Long before there were tatty, snarky blogs, the voice of amazed, bemused hilarity was baked into Mr. Kaplan’s version of the weekly. And dozens of the people annealed in his weekly oven of big ambitions and tiny budgets have been graduated onto the Web and into mainstream newsgathering, a diaspora that both widened and diluted its strength as a paper.

The Observer relies heavily on real estate advertising and circulates mostly in Manhattan to about 50,000 readers. It has undergone significant changes since it was sold by the avuncular Manhattan businessman Arthur Carter in 2006, and purchased by the Manhattan real-estate scion Jared Kushner. At the tender age of 25, Mr. Kushner plunked down almost $10 million for the weekly. The penchant for money-losing remained a part of the Observer’s identity, but in 2007, the weekly left behind its broadsheet format and became a tabloid and turned significant attention to its Web site. Mr. Kaplan said at the time that part of the gesture was to come up with a paper that its new owner could relate to.

(In some ways Mr. Kushner would appear to be more of an ideal subject than owner of the weekly. On Tuesday night, he and girlfriend Ivanka Trump walked the stairs leading up to the Vanity Fair party celebrating the opening of the TriBeCa Film Festival. The photographers went bonkers.)

Observer staffers said the pairing of the literary editor preoccupied by New York demi-mondes and the young real estate baron was an odd alliance that was bound to dissolve at some point, but Mr. Kaplan, as is often the case in public partings, had only kind words to offer.

“Jared saved the paper,” he said in the interview. “It would have gone bye-bye in 2006. He is fundamentally a capitalist in a business that needs capitalists and he is 28 years old in a business that needs 28-year-olds.”

Mr. Kaplan, a former reporter at The New York Times and once the executive producer of “The Charlie Rose Show,” came to the Observer as an editor in the tradition of Clay Felker, the late, founding editor of New York magazine. He promoted and executed an edgy brand of civic hyperbole, a belief that there was and is no other place in the world like New York City. His job, which has previously belonged to Graydon Carter, now the editor of Vanity Fair, and Susan Morrison, now an editor at The New Yorker, involved the creation of a real-time taxonomy of New York power — not just who was up and down, but who mattered in the first place. Finding oneself depicted in a large-headed caricature in the paper was a totem of arrival in some parts of Manhattan, a sign that one had become worthy of incarceration in the social pantheon defined by its pages.

But the New York Observer has always worked on a less than thin margin. Mr. Kushner may have a small interest in publishing, but his main business is New York real estate, which has been a rugged nexus of the economic downturn.

Mr. Kaplan believes that Mr. Kushner will continue to support the paper.

“It’s true that he and I are very different creatures, but he is very ambitious, which is The New York Observer’s stock-in-trade,” he said. “He clearly wants to see this thing through.”

Mr. Kaplan, who called the paper his “life’s work” when he was shopping it after Arthur Carter tired of putting tens of millions of dollars into it, said that it will continue in some form, just not with the topspin he put on it every week.

“I bring my own weird cultural framing to this, but I am not immune to the Oedipal triumph of what comes next here from the people at this paper who will take it over,” he said. “It will be a battle on all fronts, but the paper will be freer and faster, moving into the future in ways that I can’t foresee.”

Mr. Kaplan said his replacement has not yet been named.