Stephen B. Oates, a Civil War historian and the biographer of several prominent Americans, including Abraham Lincoln, the Rev. Dr. Martin Luther King Jr. and William Faulkner, died on Aug. 20 at his home in Amherst, Mass. He was 85.

His son, Greg, said the cause was pancreatic cancer.

In his best-known works, Dr. Oates explored the lives of four prominent figures — John Brown, Nat Turner, Lincoln and Dr. King — in what he called his “Civil War quartet.”

These men, he wrote in “Biography as High Adventure,” an essay published in 1986, “humanize the monstrous moral paradox of slavery and racial oppression in a land based on the ideals of the Declaration of Independence.”

He added: “All four were driven, visionary men, all were caught up in the issues of slavery and race, and all devised their own solutions to those inflammable problems. And all perished, too, in the conflicts and hostilities that surrounded the quest for equality in their country.”

It was a sign of Dr. Oates’s status in his field that Ken Burns, the filmmaker, included him in his epic 1990 PBS documentary “The Civil War.”

“Stephen was an extremely valuable adviser to our Civil War series and an informed and passionate participant,” Mr. Burns said by email. “He knew the bottom-up story as well as the top-down one, but more importantly, he knew and appreciated the huge stakes for the United States and indeed the world in a Union victory.”

Dr. Oates taught history and biography at the University of Massachusetts Amherst from 1968 to 1997, and his two-volume survey of American history educated a generation of college students.