Historian - chronicler Stephen Ambrose (born on this date in 1936) -- he died in 2002

from Writer's Almanac (American Public Media, Garrison Keillor):
January 10 is the birthday of best-selling historian Stephen Ambrose, born in Lovington, Illinois (1936). Ambrose's father was a Navy doctor during World War II, and the family followed him from post to post around the country until he was shipped overseas. The war ended, Ambrose's father came home and took up a private practice in Wisconsin, and Ambrose decided he'd take over when he grew up.
A pre-med student, he was annoyed when his state university requirements compelled him to take an American history class the second semester of his sophomore year. It was called, "Representative Americans," and was based on biographies of individuals throughout the country's history; the first class focused on George Washington. The professor said that the students would be completing their own biography of an unknown Wisconsinite, which they would have to use primary research from the state historical society to write. The result, the professor promised, would add to the sum of the world's knowledge.
"And that just hit me like a sledgehammer," Ambrose later said. "It had never before occurred to me that I could add to the sum of the world's knowledge." He changed his major to history, and at the end of the term wrote a 10-page biography of a Civil War-era one-term Wisconsin Congressman named Charles Billinghurst. Ambrose marveled that he was now the world's leading expert on Charles Billinghurst. "Now what I soon learned was, the reason for that was that nobody else cared about Charles A. Billinghurst," Ambrose laughed. But his next epiphany was what transformed him from a historian to a world-class storyteller: "But I can make 'em care if I tell the story right."
He became the biographer of Dwight Eisenhower and Richard Nixon, he wrote a best-selling book about the Lewis & Clark expedition titled Undaunted Courage (1996), and wrote multiple books on World War II, like Citizen Soldiers (1997) and Band of Brothers (1992).