On March 25, 1911, a pleasant springtime afternoon, a fire broke out in a garment factory near Washington Square in New York City's Greenwich Village. Within minutes, the entire eighth floor of the ten-story tower was full of flames. Onlookers, drawn by the column of smoke and the clamor of converging fire wagons, watched helplessly and in horror as dozens of workers screamed from the ninth-floor windows. They were trapped by flames, a collapsed fire escape and a locked door. Firefighters frantically cranked a rescue ladder, which rose slowly skyward—then stopped at the sixth floor, fully extended. Pressed by the advancing blaze, workers began leaping and tumbling to their deaths on the sidewalk. Other workers perished in the flames, still others plunged into an open elevator shaft, while behind the factory two dozen fell from the flimsy fire escape. In all, 146 workers, most of them immigrant young women and girls, perished in the Triangle Shirtwaist Factory fire. For 90 years it stood as New York's deadliest workplace disaster.

This story—and the fire's impact on the politics of New York and the nation—took hold of me in the early 1990s. I had moved to the Village as a reporter for the Miami Herald, and one day, while exploring the neighborhood, I was surprised to find the factory tower still standing at the corner of Washington Place and Greene Street. In the years that followed, I often passed that corner and always paused to look up at those ninth-floor windows.

My curiosity led me to a spare and forceful book, The Triangle Fire. Written by a labor organizer named Leon Stein and published in 1962, the book was both harrowing and somewhat frustrating. Stein had interviewed dozens of survivors, tracked down a number of original records and rendered the story in taut prose. But many of the questions that most interested me were taken for granted by Stein, who spent his career in the New York garment industry, a world stamped by the Triangle tragedy. I was hungry for more about the context and characters surrounding this event, which influenced such momentous figures as the progressive New York governor Alfred E. Smith, the New Deal architect Senator Robert F. Wagner and the pioneering Secretary of Labor Frances Perkins. But no full-length study of the fire and its impact on politics had been written in the decades after Stein's book.

So I proposed to write my own.

How rash! But my folly dawned on me slowly—and only after I had blown a substantial stack of my publisher’s advance on diapers, formula and preschool tuition. I discovered that virtually all the key documents concerning the Triangle fire had been lost or destroyed. Records of the fire marshal’s investigation: long gone. Files of the coroner's special jury: vanished.

Worst of all, I couldn't find the official transcript of the trial of Isaac Harris and Max Blanck, the Triangle factory owners, who had been charged with manslaughter on the theory that their negligence caused the workers' deaths. Their three-week trial in December 1911 collected sworn testimony from more than 150 witnesses who were questioned while details of the disaster were still relatively fresh in their minds. Dozens of survivors, including Harris and Blanck themselves, recounted their narrow escapes, while firefighters, police officers and building engineers added details of the factory layout and the fire's awful progress. No other document could take me closer to that factory in the moments before and after the fire erupted.

I knew that a transcript had been prepared, because Stein had used it in his research: his notes were part of the labor history archive at the Kheel Center at Cornell University. Yet when I contacted the New York City archives, I was told that, well, the transcript—all 2,000-plus pages—seemed to have been lost. It apparently vanished, wouldn't you know, during a project to preserve historic documents. Sometime around 1970, an archives official explained, New York's John Jay College of Criminal Justice received a grant to transfer important court records to microfilm. Somewhere between the courthouse and the college, the Triangle record was lost forever.

Still, I figured there must be other copies, prepared for the prosecutor or the defense attorney. I inquired at other New York colleges and universities, at the New York Public Library, at various city museums and state archives. Coming up empty, I turned to the multitude of daily newspapers from 1911. Surely the sensational trial of Harris and Blanck must have been covered extensively, in front-page stories full of colorful details and verbatim testimony.

Nope. My heart sank as I fed rolls of microfilm into reading machines at the Library of Congress (having moved to Washington as a reporter for the Washington Post). There was next to nothing in the New York World, the American, the Herald, the Times, the Tribune, the Post. Only the most dramatic testimony and the verdict—not guilty—registered more than a few paragraphs stashed in the back pages.

My frustration turned to panic. Samuel Johnson famously declared that "no man but a blockhead ever wrote, except for money," and I have never been wealthy enough to test his theory. The money I had taken was now gone, even as the bills continued to arrive. I began to lose hope that I could actually make a book from the scraps and remnants I had been compiling.

Which was sad, because some of the scraps were fascinating. Virtually nothing had been known about the young women who worked and died in the Triangle factory, but I was finding whispers of their brief stories in old census records and city maps. The microfilmed record of a Socialist newspaper in New York, the Call, contained a haunting half page of photographs of Triangle fire victims, lent by their grieving families. The same newspaper fleshed out Harris and Blanck's role in resisting efforts to unionize the garment factories.

Such discoveries kept me plodding along, despite flagging hopes. One spring day in 2001, almost exactly 90 years after the fire, I turned my attention at the Library of Congress to the high-priced attorney Harris and Blanck hired to save them from prison. Max D. Steuer was among the most colorful figures in the peacock gallery of New York before World War I. An immigrant and former sweatshop worker, Steuer rose to the pinnacle of the New York bar, starring as courtroom magician in dramas ranging from celebrity sex scandals to securities frauds to the disputed wills of dysfunctional dynasties. He became known as "Million-Dollar Steuer" in the Hearst newspapers until he complained about it to one of his clients: William Randolph Hearst. The Triangle trial—specifically, Steuer's cunning cross-examination of the star prosecution witness—was a key moment in his legendary career.

I found a sketch of Steuer's life in the Dictionary of American Biography, published in the early 1960s. The entry ended with a list of sources printed in tiny type. One note caught my eye: "Collections of the records and briefs of cases in which Steuer appeared are in the N.Y. County Lawyers' Assoc." What records?

I looked up the NYCLA on the Internet and was pleased to find that it still existed. It had been founded early in the 20th century as an alternative to the Association of the Bar of the City of New York, which—in those days—was not open to women, blacks or Jews like Steuer. A few calls led me to Ralph Monaco, director of the NYCLA library, who seemed genuinely interested in my saga—and genuinely sorry to tell me he had no idea what records the Dictionary was talking about.

That was the low point.

Three days later, Monaco called back. He had posted a listserv message explaining my plight to the Law Librarians Association of Greater New York. One of his predecessors as director of the NYCLA library, Alison Alifano, saw the message and replied that a collection of Steuer’s records was somewhere in the library. She just was not sure where. Then a veteran library employee named Jose Rosario unearthed what appeared to be a transcript from the stacks.

I told Monaco I could be in New York the next day.

How about next week? he countered. Promptly at 9 the next Monday morning, I entered NYCLA's downtown headquarters, an elegant Cass Gilbert landmark in the twin shadows of the World Trade Center towers. On Monaco's desk, I finally laid eyes on my prize: two fat, antique, leather-bound tomes, labeled Vol. 1 and Vol. 3. Vol. 2 appeared to be missing, so Rosario and I went back to the stacks to hunt for it. He led me to a shelf of similar books, all from Steuer's estate. Scanning the spines, I realized that he had commemorated his greatest trial victories by binding his carbon-copy transcripts in gold-lettered leather. Upon his death in 1940, he bequeathed these trophies to NYCLA. And as his fame had faded with the passing decades, they were relegated to storage and forgotten.

We never found the missing volume, but that hardly dampened my excitement as I turned the first of more than 1,300 pages of recovered history. For much of the next two weeks, I read slowly through the sometimes tangled testimony and typed thousands of words of notes and quotations into my laptop. Photocopying the volumes was out of the question—the cheap paper, nearly a century old, was crumbling between my fingers. In fact, I began to worry that Monaco would call a halt to my reading because the books were falling apart. So I sat at a table as far from the reference desk as I could get, and swept small drifts of paper crumbs into my briefcase to hide them.

Each morning, however, Monaco and his colleagues welcomed me back. And gradually I learned not only what it was like to endure the fire but also what it was like to work at the Triangle Waist Co. Notorious today as a classic sweatshop, the Triangle was a model of modern efficiency to its owners and employees. Indeed, as I came to understand the factory, the pace of daily work and the intricate relationships inside the large, family-run business, I could see how the factory's scale and efficiency helped cause the tragedy. Specially designed bins held hundreds of pounds of scrap cotton and tissue paper at a time. In one of these bins, just before the quitting bell rang, a fire kindled. The supply of fuel turned the factory into what a fire captain called "a mass of traveling fire" within 15 minutes.

Some testimony was spellbinding, such as factory foreman Samuel Bernstein's marathon account of his efforts to fight the fire and save the workers. Capt. Howard Ruch of the New York Fire Department told of his initial survey of the charred ninth floor. "I stepped on something that was soft," he said, and only then realized he had reached a pile of bodies. Line by line, the transcript restored history to three dimensions and provided a Rosetta stone for understanding Leon Stein's notes from the lost volume of testimony.

Through the cooperation of NYCLA and Cornell, my experience of reading the lost transcripts is now available to anyone with an Internet connection. In 2004, Kheel Center director Richard Strassberg carried the Steuer volumes to the Ithaca campus, where each page was scanned and digitized. Because the quality of the originals was so poor, the process captured only about 40 percent of the text. So Patricia Leary of the Kheel Center painstakingly corrected every page.

Last autumn, after more than a year of effort, the Kheel Center posted the entire text on its Triangle fire Web site: ilr.cornell.edu/trianglefire. The site, which receives some six million visitors each year, is a model for archivists who want to make their records available to students and researchers. By June, portions of the recovered record had been downloaded more than 1,100 times, Strassberg reports, including nearly 400 complete copies.

The Triangle fire catalyzed reforms in New York that spread nationwide—outward-swinging exit doors and sprinklers in high-rise buildings, for example. These reforms in turn fueled the careers of people like Smith and Wagner and Perkins, the first woman to serve in a presidential cabinet. Half a century after the fire, she still pointed to that day as the birth of the New Deal. Today, the memory of the fire moves reformers to wonder why some workers in the United States—and many more abroad—still toil in needlessly dangerous conditions.

Those who experienced the horror firsthand could not have anticipated the impact. Nor could they have imagined that, someday—thanks to a lawyer's vanity, a buried footnote, a diligent librarian and the power of technology—their long-silent voices could speak directly of their experiences to readers around the world.

David Von Drehle wrote Triangle: The Fire That Changed America.