“Nothing good was ever written in a large room,” David McCullough says, and so his own office has been reduced to a windowed shed in the backyard of his Martha’s Vineyard home. Known as “the bookshop,” the shed does not have a telephone or running water. Its primary contents are a Royal typewriter, a green banker’s lamp, and a desk, which McCullough keeps control over by “flushing out” the loose papers after each chapter is finished. The view from inside the bookshop is of a sagging barn surrounded by pasture. To keep from being startled, McCullough asks his family members to whistle as they approach the shed where he is writing.

In its simplicity and modesty, the bookshop is characteristic of an author who prefers to deflect credit for his success—to his material, to his family members, to his upbringing. McCullough’s wife Rosalee was present throughout the interview. We were sitting in the McCulloughs’ low-ceilinged living room, which became progressively darker as the tape recorder rolled on, so that by the end of the afternoon, with the lights off, only the nineteenth-century library across the street was clearly visible. During the entire time, almost eight hours, McCullough spoke vigorously and quickly, growing hoarse but never seeming tired.

In person the sixty-six-year-old McCullough is somewhat different from the image projected on public television, where he frequently hosts and narrates programs. The voice, coming out of shadows across the room, was full of emotion. His face seemed longer, his eyes larger. He gestured often, sometimes calling attention to nearby objects, such as a piece of cable from the Brooklyn Bridge. At the end of the meeting, he issued an impromptu dinner invitation and whipped up a delicious pasta with clam sauce, one of his specialties.

McCullough was born in Pittsburgh in 1933 and grew up in the boom years of World War II steel production. He attended Yale, where he studied English and visual arts, and got a job at Sports Illustrated in New York after graduation. During the 1960s he edited and wrote for American Heritage magazine and briefly worked for the United States Information Agency. His first book, The Johnstown Flood (1968), was not published until McCullough was thirty-five and already married with several children.

He has won the Pulitzer Prize, two National Book Awards, the Francis Parkman Prize and dozens of other honors, and not a single one of his books—including Truman (1992), The Great Bridge (1972), and The Path Between the Seas (1977)—has ever been out of print.

INTERVIEWER

Would you tell us about the motto tacked over your desk?

DAVID McCULLOUGH

It says, “Look at your fish.” It’s the test that Louis Agassiz, the nineteenth-century Harvard naturalist, gave every new student. He would take an odorous old fish out of a jar, set it in a tin pan in front of the student and say, Look at your fish. Then Agassiz would leave. When he came back, he would ask the student what he’d seen. Not very much, they would most often say, and Agassiz would say it again: Look at your fish. This could go on for days. The student would be encouraged to draw the fish but could use no tools for the examination, just hands and eyes. Samuel Scudder, who later became a famous entomologist and expert on grasshoppers, left us the best account of the “ordeal with the fish.” After several days, he still could not see whatever it was Agassiz wanted him to see. But, he said, I see how little I saw before. Then Scudder had a brainstorm and he announced it to Agassiz the next morning: Paired organs, the same on both sides. Of course! Of course! Agassiz said, very pleased. So Scudder naturally asked what he should do next, and Agassiz said, Look at your fish.

I love that story and have used it often when teaching classes on writing, because seeing is so important in this work. Insight comes, more often than not, from looking at what’s been on the table all along, in front of everybody, rather than from discovering something new. Seeing is as much the job of an historian as it is of a poet or a painter, it seems to me. That’s Dickens’s great admonition to all writers, “Make me see.”

INTERVIEWER

Have you had Scudder moments?

McCULLOUGH

Oh, yes. I suppose the most vivid one—when I actually felt something like a charge of electricity run up my spine—was while working on the puzzle of young Theodore Roosevelt’s asthma. Hoping to pin down the cause of his attacks, I had been talking to a physician who raised such questions as whether there was a dog or a cat in the house or if the attacks occurred during the pollen season. Then a specialist in psychosomatic aspects of the illness suggested a different approach. Did the attacks come before or after some big event? Or before the boy’s birthday, or the night before a trip, or just before or after Christmas? Using his diary entries, I made a calendar of what he was doing every day. In pencil I wrote where he was, who was with him, what was going on, and in red ink I put squares around the days of the asthma attacks. But, a little like Scudder and the fish, I couldn’t see a pattern. Then first thing one morning, without really thinking about it, I looked at the calendar lying on my desk, and I saw what I’d been missing. The red boxes were all in a row—the attacks were all happening on Sunday. I thought, What happens on Sunday? Then it began to make sense. If he had an attack, he didn’t have to go to church, which he hated, and his father would take him to the country. He loved the country, and when it was just he and his father alone—that was pure heaven. This doesn’t mean the attacks were planned. The closest analogy to an asthma attack might be a case of the hiccups—you don’t decide to have them, and yet just as the hiccups can be ended by something traumatic some kinds of asthmatic attacks are triggered by anxiety. Roosevelt paid an awful price for those trips because attacks such as he had were horrible. There may well have been other things contributing to the attacks, but the Sunday pattern was too pronounced to be coincidental.

There’s another scene in Mornings on Horseback that I felt was crucial to understanding Roosevelt’s character, which might not be considered important by conventional standards. The family was taking a trip up the Nile and young Theodore, who was an amateur taxidermist, shot and stuffed a number of birds. So I went out and found out how taxidermy is done. It takes patience and dexterity, and it’s smelly and grubby—a kind of work that would be very difficult for a child. And if you do it on a boat with your whole family present, you upstage them all. There’s a paragraph or two in the book about the process of stuffing a bird, because I thought that would show a lot about the boy. I didn’t want to say, He was a bright boy who did things other boys couldn’t. I wanted the reader to know it.

Novelists talk about their characters starting to do things they didn’t expect them to. Well, I imagine every writer of biography or history, as well as fiction, has the experience of suddenly seeing a few pieces of the puzzle fit together. The chances of finding a new piece are fairly remote—though I’ve never written a book where I didn’t find something new—but it’s more likely you see something that’s been around a long time that others haven’t seen. Sometimes it derives from your own nature, your own interests. More often, it’s just that nobody bothered to look closely enough.

INTERVIEWER

What led you to become a writer?

McCULLOUGH

Thornton Wilder was a fellow at my college at Yale. Here was a world-celebrated writer for us to talk to, to have lunch with—imagine!—and he was easy to talk to, delightful. Later, while working in New York, I read the interview with him in The Paris Review. I can’t tell you what a difference it made for me. When asked why he wrote books and plays, he said, “I think I write in order to discover on my shelf a new book that I would enjoy reading or to see a new play that would engross me.” If it didn’t exist, he wrote it so he could read it or see it.

INTERVIEWER

What were you doing in New York?

McCULLOUGH

After graduation I got a job at Time-Life, as a trainee at Sports Illustrated, a new magazine. I worked there and on others of the Time-Life magazines for five years, and for a number of different editors. One of them had a big rubber stamp and a red ink pad. The stamp had a four letter word on it and if he didn’t like what you’d written, he’d stamp it and send it back. The word was dull. When you’d had that done to you a couple of times, you began to get the point.

Earlier, as a graduation present, I’d been given A Stillness at Appomattox by Bruce Catton. And though I didn’t know it at the time, that book really changed the course of my life. I thought it was just marvelous and wondered, How do you do that? I read more of Catton and other books about the Civil War. Margaret Leech’s Reveille in Washington stands out in memory. I was finding my way, I suppose.

INTERVIEWER

When did you decide, to use Thornton Wilder’s words, to “write the book you wanted to read”?

McCULLOUGH

It was when I came across a set of old photographs of the Johnstown flood. When we were little kids, we used to make a lake of gravy in our mashed potatoes; then we’d take a fork, break the potatoes, and say, The Johnstown flood!—with no idea why in the world we did it. That was about all I knew about it until I saw the photographs of the flood, quite by chance at the Library of Congress. I became extremely curious to know what had happened and why. I went to the library and found a book, and it was only so-so. The author had some of the geography of western Pennsylvania wrong, I could see, and he didn’t answer certain questions I felt he should have. I took out another book, a potboiler written at the time of the disaster, and it was even less satisfactory. So I decided to try to write the book I wanted to read. I wasn’t at all sure how to go about it. One evening, in New York, at a gathering of writers and historians interested in the West, my boss, Alvin Josephy, pointed to a white-haired man across the room. He said, That’s Harry Drago. Harry Sinclair Drago. He’s written over a hundred books. I waited for my chance and walked over. Mr. Drago, I said, Alvin Josephy says that you’ve written over a hundred books. Yes, he said, that’s right. How do you do that? I asked. And he said, Four pages a day. Every day? Every day. It was the best advice an aspiring writer could be given.

I wrote The Johnstown Flood at night after work. I would come home, we’d have dinner, put the kids to bed, and then at about nine I would go to a little room upstairs, close the door, and start working. I tried to write not four but two pages every night. Our oldest daughter remembers going to sleep to the sound of the typewriter.

INTERVIEWER

What kind of research did you do for that book?

McCULLOUGH

Well, one of the great resources I came across was testimony taken by the Pennsylvania Railroad from their employees after the flood. It was done in anticipation of lawsuits. They brought people in and sat them down and said, Tell us what you saw and what you did. Thus we’ve been left with many reports of the disaster from a cross section of the population, all in their own words.