And there was “Breakthrough! How Three People Saved ‘Blue Babies’ and Changed Medicine Forever” (2015), about a groundbreaking heart operation performed in 1944 and credited to two white doctors, Alfred Blalock and Helen Taussig, though important parts of the procedure were the work of a Black research assistant, Vivien Thomas, who many at the hospital, Johns Hopkins in Baltimore, thought was a janitor.

Mr. Murphy did not mince words regarding Dr. Blalock’s failure to include his Black assistant when taking credit for the operation.

“Blalock could have pushed his talented research assistant’s career forward with little trouble, and he could have fended off any criticism hurled at him,” he wrote. “But he didn’t. Instead, Blalock was, like too many people in positions of power, happy to allow an unfair situation to drift along.”

In these and other books, Mr. Murphy relied heavily on first-person accounts, many of them by ordinary people rather than generals or presidents. It was an approach he latched onto early in his writing career. He was contemplating a book on the history of tractors, until his father mocked the idea as too boring.

“And I realized that an interesting thing about tractors, especially steam tractors, is that they exploded a lot,” he told Publishers Weekly. “So I wrote a history of tractors, knitting together firsthand accounts of people who had survived tractor explosions.”

The resulting book, “Tractors: From Yesterday’s Steam Wagons to Today’s Turbocharged Giants,” was published in 1984 and did well.

“I realized that the key was the firsthand perspective,” he said.

James John Patrick Murphy was born on Sept. 25, 1947, in Kearny, N.J., to James and Helen (Grasso) Murphy. In addition to history books, he sometimes wrote fiction, and in one of those works, “Revenge of the Green Banana” (2017), he drew on his experiences at St. Stephen’s School in Kearny to tell the story of a sixth grader named Jimmy Murphy who seeks revenge on a teacher for casting him in a school play as a banana. He wrote this in the dedication:

“To all the teachers at St. Stephen’s, each and every one. I want to apologize for what I did and thank you for putting up with my antics for so many years. I entered St. Stephen’s as one sort of kid and left as an entirely different one.”