On May 30, 1899, Wilbur Wright sat down at a small desk in the house that he shared with his brother, sister and father and wrote one of the most important letters of his life. “Indeed, given all it set in motion, it was one of the most important letters in history,” David McCullough writes in his newest book, The Wright Brothers, to be released Tuesday by Simon and Schuster.

In the letter, addressed to the Smithsonian Institution in Washington, D.C., Wilbur noted his lifelong interest in flight and his firm conviction that “human flight is possible and practicable.” He announced his plans to begin a “systematic study” and asked the Smithsonian for any material they had published on the subject, along with a list of related works in print.

The historian still works on an old Royal typewriter. — Ivy Ashe

Four years later, in 1903, the Wright Flyer (now hanging in the Smithsonian National Air and Space Museum) became the first mechanically powered machine to achieve controlled flight with a pilot aboard. That first powered flight, at Kitty Hawk in North Carolina, lasted about 12 seconds and covered about 120 feet. Later in the day, Wilbur and the Wright Flyer remained airborne for nearly a full minute.

Mr. McCullough, a Pulitzer Prize-winning historian and longtime resident of West Tisbury, has also long been fascinated with mechanical flight, he told the Gazette in a phone interview this week. He took his first flight lessons on the Vineyard in the 1960s, at a former airfield in Oak Bluffs. He couldn’t afford to pursue his license at the time, but loved flying the Piper J-3 Cub, a small, chrome-yellow aircraft produced between 1937 and 1947. He also remembers co-piloting a plane from Washington, D.C., to Ohio with John Glenn, who in 1962 became the first American to orbit the Earth.

The story of the Wright brothers, as told by Mr. McCullough, is a lesson in self-reliance, perseverance, family values and hard work. Wilbur and his younger brother Orville were largely self-educated, benefitting from the encouragement of their father, the preacher Bishop Milton Wright, who kept the family library in Dayton, Ohio, well stocked with classics, along with books on history, art and culture. When the brothers went to France to showcase their invention in 1908, Mr. McCullough said, Europeans were stunned that they had never finished high school.

Several books have been written on the Wright brothers and their accomplishments, but none have so deeply explored their personal and family life. Their younger sister, Katharine, an Oberlin College graduate and high school teacher, figures prominently in the brothers’ success, offering constant support and serving as a spokesman when the brothers became famous. “I think she is an extremely interesting, admirable character,” Mr. McCullough said. “And I’m not sure that their efforts would have come out the way they did had it not been for her.” Milton, referred to mostly as “the Bishop,” also plays an important role, helping to instill in his children a love of reading, and maintains a presence throughout much of the book.

“I’m a great believer in giving credit where credit is long overdue,” Mr. McCullough said.

Mr. McCullough's book will be available at Bunch of Grapes Bookstore on May 5.

All the Wrights had a gift for writing and corresponded with each other often. They left behind thousands of pages of letters and diaries that are preserved in the Library of Congress and the National Archives, where Mr. McCullough did much of his research, with the help of an assistant in Washington, D.C. He also relied heavily on historians at the Smithsonian Institution, where he had some history of his own. In the 1980s, he hosted the popular TV series Smithsonian World.

His research brought him to Kitty Hawk, on the Outer Banks of North Carolina, where the brothers conducted their first test flights, to Le Mans in France, where the world finally took note of their achievement, to Dayton, and elsewhere. In his diaries, Wilbur describes the tops of buried trees poking out from the sand at Kitty Hawk — an image that Mr. McCullough said brought to mind the south shore of Chappaquiddick.

The author did much of his writing in West Tisbury, in the Music street house that he and his wife Rosalee bought 50 years ago. As with all of his books, he composed The Wright Brothers entirely on the old Royal Standard typewriter that he bought second-hand in 1965. “It’s 75 years old and there is nothing wrong with it and there has never been anything wrong with it,” he said. “I have to change the ribbon, that’s about all.”

Despite his fascination with technology and innovation, he has never tried to compose on a computer. “The material that I work with, that I need, isn’t on the computer,” he said. “It’s in the libraries and archives and museums. People say to me, don’t you realize how much faster you could go? Well, of course I do. But I don’t want to go faster. If anything I want to go slower.”

Mr. McCullough sees The Wright Brothers as part of a trilogy of sorts that began in 1977 with The Path Between Seas, his book about the construction of the Panama Canal, and continued in 1983 with The Great Bridge, about the building of the Brooklyn Bridge. All three achievements surpassed anything up until then, he said, and “were done against extreme adversity, unpredictable surprise defeats and failures. But they were all achieved by people who would not give up.”

The backdrop to the Wright brothers’ achievement was Dayton, Ohio, a thriving factory town and a hotbed of invention at the turn of the century. Mr. McCullough writes that Dayton ranked first in the country in new patents, relative to its population. It was “a tremendously invigorating, inspiring atmosphere,” he said. And the two brothers — founders of the Wright Cycle Company in the 1890s and innovators by nature — were well positioned to succeed.

Unlike some of their contemporaries, they had a highly methodical and calculated approach to solving the problems of flight. “They would take risks when necessary, but they were no daredevils out to perform stunts and they never would be,” Mr. McCullough writes. They were also practical: Only one brother would fly at a time, so that if he died in a crash the other could continue the experiments.

“What I hope my book conveys is that the Wright brothers were far more than just a couple of clever bicycle mechanics — good old boys from the Middle West — who got lucky and invented the airplane,” Mr. McCullough said. “This is an amazing and important American story that everybody ought to understand and take pride from — take advice from and take lessons from. I know I do.”

Mr. McCullough was 15 in 1948 when Orville Wright died at the age of 76. (Wilbur died from typhoid in 1912, at the age of 45.) “It may seem to some like a long, long time ago, but as history goes it’s just the other day,” Mr. McCullough said. “And yet the world has changed so immensely because of their invention.” Like many people alive today, Mr. McCullough has witnessed much of the evolution of flight, from the Piper J-3 Cub (which Orville himself once flew as part of a war bond campaign) to the Orion spacecraft, which is being developed for deep-space travel.

Where will that evolution lead in another 50 or 100 years? “Impossible to say,” Mr. McCullough said. “I’m a strong believer that there is no such thing as the foreseeable future: There are too many surprises in store.”

The Wright Brothers, by David McCullough, published by Simon and Schuster, will be available at Bunch of Grapes bookstore on May 5. Mr. McCullough will speak about the book at the West Tisbury Grange on July 14 at 7 p.m.