NEW YORK (AP) — Robert A. Caro stands between two giant columns in a second-floor library of the New-York Historical Society, looking out on dozens of friends, family members and colleagues. A research room named for him looms behind. Portions of his archives are on display nearby.

“The most honest thing I could possibly say tonight is also possibly the corniest, and that is having my archives here is, in a way, a dream come true,” the historian said during a recent dinner tribute at the Society, a 200-year-old institution located opposite Central Park that he would visit often as a child who already imagined becoming a writer.

“I won’t say I dreamed of being a well-known writer,” he added. “But my dreams were of being a writer. So now, I am a writer and my papers are here, and you could say it’s a dream come true.”

The 88-year-old author spends most of his days writing — the fifth and final volume of his Lyndon Johnson series, more than a decade in the making, is still without a scheduled release date. But in recent weeks, he has been looking back to his first book, to the biography that made him famous, and, for some, infamous: “The Power Broker.” His Pulitzer Prize-winning chronicle of Robert Moses is a page-turning — around 1,300 pages — appraisal of the New York City municipal builder, portrayed by Caro as a man of historic vision and talent whose ego and disregard for others made him a cautionary tale for unchecked authority.

A New Yorker for much his life, Caro is the Society’s unofficial laureate, subject of one exhibit — “Turn Every Page” — about his famously thorough research and a new one dedicated to “The Power Broker,” published 50 years ago. “Robert Caro’s The Power Broker at 50” includes typescript pages, notebook entries, letters, press clippings, a draft of the book’s introduction and samples of Caro’s reporting, including a tally sheet that he and his wife, Ina, amassed of commuters to Long Island’s Jones Beach, Moses’ first major public project.

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Caro’s book remains widely purchased, taught and discussed, and so much a symbol of serious thought that it turned up in the background of many Zoom interviews with journalists and public figures during the height of the pandemic. The Society not only sells signed copies of his books, but also offers ceramic mugs that read: “I FINISHED THE POWER BROKER.”

Although “The Power Broker” is among the longest one-volume books in existence, Caro obsessives — and the author himself — have wondered about the material left out. Caro’s original manuscript was around 1 million words, and some 300,000 had to be removed by Caro and editor Robert Gottlieb just so the book wouldn’t require an extra edition. Missing or drastically cut sections include one on community activist Jane Jacobs, who helped stop Moses’ efforts to build a highway through Greenwich Village, and one on tenants of a Bronx neighborhood uprooted by the Cross Bronx Expressway.

Caro himself has long forgotten what happened to the old manuscript pages, boxed up and placed in filing cabinets decades ago and opened only after the Society acquired his papers in 2020. The exhibit, and his archives, now open to the public, offer few clues.

According to Valerie Paley, senior vice president and director of the society’s Patricia D. Klingenstein Library, virtually all “The Power Broker” papers have been sorted and no sign of a Jacobs section or One Mile sequel has been found. The society’s online site dedicated to the archive lists thousands of “Power Broker”-related materials, but nothing specific about Jacobs or the lives of the Bronx tenants after they left.

During a recent interview at his writing office, a short walk from his apartment and the Society, Caro noted one artifact in the exhibit — a napkin on which he had scrawled a few thoughts about “Fiddler on the Roof” and a line about growing up knowing everyone you meet. He had been speaking with some Bronx women displaced by Moses’ highway and noted how their fates could be compared to those driven out in Russia by the czar. But what he had hoped would be a long chapter on what happened to them ran just 10 pages.

“I remember writing pages of that chapter over and over again,” he said. ““I thought it was good, but we were coming down to the end and we had to cut another 40,000 words and it had to go.”

“The Power Broker” set the template for Caro’s grand ambitions and flexible deadlines. He thought he would spend a few months on the book, but needed more than seven years, taking so long that he and Ina ran out of money and had to sell their home. His background was in journalism; he was a Pulitzer-winning investigative reporter for Newsday. But “The Power Broker” was also influenced by some of the 19th century novelists he admired, notably Anthony Trollope, whom his wife first told him about.

Caro’s narrative has the kind of scale, moral underpinning, political insights and outsized characters — Moses above all — that he admired in such Trollope works as “The Prime Minister.” Asked if “The Power Broker” could almost be called a nonfiction 19th century novel, Caro responded: “Not almost.”

When “The Power Broker” was published, Moses issued a 23-page statement denouncing it as full of “mistakes, unsupported changes” and “random haymakers” and accused Caro of listening too closely to “a few bellyachers on street corners” and “disgruntled truck drivers.” But most critics regarded the book as a revelation and continue to rank it as essential for those interested in politics, urban planning or New York history. Admirers include President Barack Obama, who recalled being “mesmerized” by it when he awarded Caro a National Humanities Medal in 2010.

Even Jacobs forgave him for not mentioning her. In a 1974 letter displayed in the exhibit, she thanked Caro for sending her a copy and expressed gratitude for his efforts.

“I have no doubt that many readers are going to feel the way I do — we owe you a tremendous debt for all those years of hard work, good sense, unflagging curiosity, and compassion,” she wrote. “What an account it is of human predicaments; it ranks with the great novels.”