Edward L. Kimball, whose biographies of his father provided a unique window to the process that led to the landmark 1978 revelation that ended the Mormon practice of restricting the priesthood from black men, died Monday at age 86.

Late LDS Church President Spencer W. Kimball told his son that the revelation extending the priesthood to all worthy men in the church and temple blessings to all worthy men and women was "the most important thing to happen in the church since the Manifesto" — the 1890 declaration which was the beginning of the end of the practice of polygamy in The Church of Jesus Christ of Latter-day Saints.

"Edward was a thoughtful, intelligent man who focused on challenging subjects and found a great deal of satisfaction in plumbing them," said his cousin, Rick Turley, a historian and the new managing director of the church's Public Affairs Department. "The piece he wrote on the 1978 priesthood revelation is one of the best accounts of that key event in church history."

Edward Kimball died Monday in Provo, Utah. Trained as an attorney at the University of Utah, he was a law professor at Montana State University and the University of Wisconsin before becoming a member of the original faculty of the J. Reuben Clark Law School at Brigham Young University in 1973. He retired from BYU in 1995. Turley was a BYU law student during those years and said his cousin was well-liked by students.

He published his first biography of his father, "Spencer W. Kimball," in 1977, with his nephew Andrew Kimball. In 2005, he published "Lengthen Your Stride," about his father's time as the church's president and prophet.

"I think those books were really significant because it's been fairly tough to do a church history on really recent topics like President Kimball," said historian Matthew Bowman, author of "The Mormon People: The Making of an American Faith." "Edward Kimball had unique resources and access. Nobody but him probably could have written 'Lengthen Your Stride.'"

His article "Spencer W. Kimball and the Revelation on the Priesthood" was published by BYU Studies in 2008 and is available for free at byustudies.byu.edu. The article was footnoted in the church's 2013 Gospel Topics essay, "Race and the Priesthood," that explained the origin and history of the priesthood restriction.

Edward Kimball suffered from polio during his childhood in Safford, Arizona. When he was 13, his father was called as an LDS apostle and the family moved to Salt Lake City, Utah. Kimball served a Mormon mission in the Netherlands, then met Evelyn Bee Madsen at the U., where she was a secretary to the dean of the law school. They married in 1954 and raised seven children. Evelyn Kimball died in 2012.

Kimball graduated at the top of his U. law school class, then earned a doctorate of law at the University of Pennsylvania before launching his career as a law professor.

On the website Mormon Scholars Testify, Kimball provided a brief anecdote about a turning point that took him from skeptical teenager to believing adult.

He wrote a book about his mother, "Camilla: A Biography of Camilla Eyring Kimball." Camilla Kimball's brother is father of President Henry B. Eyring, now first counselor in the LDS Church's First Presidency.

Edward Kimball also edited two other books by or about his father, "Faith Precedes the Miracle" and "The Teachings of Spencer W. Kimball."

His history of the revelation on the priesthood shows the practice of the ministry of a man considered by Mormons to be a modern-day prophet. He mentions that by 1973, historian Lester Bush had published an exhaustive review of the history and concluded that the priesthood restriction dated back to Brigham Young, a fact confirmed by the church's 2013 essay.

His son's history shows President Kimball began to pray about the priesthood restriction years before the revelation, before he became church president in 1973. In June 1977, he invited three apostles, including today's church president, Thomas S. Monson, to write memos to him on the subject of blacks and the priesthood, which they did.

On June 1, 1978, President Kimball called a meeting of the First Presidency and Quorum of the Twelve Apostles in the Salt Lake Temple. The men counseled about the issue, then had a prayer circle around the altar of the temple. The answer to prayer came that the priesthood should be extended to every faithful, worthy man in the church.

"It is," Edward Kimball recorded President Kimball telling his daughter, Olive Beth Kimball, "the most earthshaking thing that has happened in my lifetime."

Turley said Kimball's biographies resonated because he managed to maintain a scholarly distance while writing about a close relative.

Initially, Edward Kimball's history about the priesthood revelation was included on a CD-ROM issued with "Lengthen Your Stride." An updated version of the biography, published in 2010, included the entire story.

Bowman said Kimball's history of the revelation was a perfect example of his unique addition to LDS Church history.

"Not only did it describe the process of decision-making," Bowman said, "it described the process of religious experience, which has been something that over the 20th and 21st centuries has been kept very private, indeed within the LDS faith. Edward Kimball's contribution has been invaluable for scholars and lay members."

Funeral details are to be determined.