Elizabeth Brown Pryor, a former State Department official and author of biographies of Clara Barton and Robert E. Lee. (Family photo)

Elizabeth Brown Pryor, a former State Department liaison on Capitol Hill who had a second career as a historian and author of well-regarded biographies of American Red Cross founder Clara Barton and Confederate Gen. Robert E. Lee, died April 13 in a car accident near her home in Richmond. She was 64.

According to published accounts, her car was struck from behind at a high rate of speed on a Richmond street, and she died at the scene. Richmond authorities charged the driver of the other vehicle, Robert S. Gentil, with involuntary manslaughter.

Ms. Pryor began her career as a U.S. Park Service ranger giving tours of the Washington Monument and later worked as a Park Service historian before joining the State Department in 1983.

In the 1990s, Ms. Pryor was among the first U.S. diplomats to reenter Sarajevo after the Bosnian War, surviving hunger and other hardships in the ravaged Bosnian capital. She later participated in arms reduction negotiations and became the spokesman for the State Department’s mission at NATO headquarters in Brussels.

“She could speak eloquently of complex matters to people in German, French and Spanish,” Barbara J. Stephenson, a former U.S. ambassador to Panama and deputy chief of mission in London, said Wednesday in an interview. “She was so often the most talented person in the room.”

Ms. Pryor was the author of the State Department’s official policy recommendation — known as the “Pryor Paper” — that led the United States to rejoin UNESCO in 2003, nearly 20 years after withdrawing from the United Nations’ educational and cultural arm. She was a State Department foreign affairs adviser to members of Congress from 2002 to 2005, when she retired to concentrate on her second career.

Her first book, “Clara Barton: Professional Angel,” came out in 1987, while she was with the Foreign Service in South Africa. Twenty years later, she published “Reading the Man: A Portrait of Robert E. Lee Through His Private Letters,” a revelatory study of the commander of the Confederate army during the Civil War.

Ms. Pryor was the first scholar to gain access to a newly discovered trove of Lee family documents that had been stored in a bank vault for decades.

In 1917, Lee’s daughter, Mary Custis Lee, sent two trunks of letters and other artifacts to the Burke & Herbert Bank in Alexandria, Va. She died the next year, and the trunks were not opened until 2002.

The materials allowed Ms. Pryor to draw a fresh, nuanced portrait of Lee, who had long been seen either as a traitor to the United States, which he had served as an Army officer, or as the lionized leader of the South’s “lost cause.”

It was hardly inevitable, Ms. Pryor concluded, that Lee would take command of the Confederate army. She pointed out that 40 percent of Virginia-born military officers sided with the Union and that Lee was often opposed on the battlefield by his own cousins.

“He is a very complex, vulnerable, engaging yet troublesome human being,” Ms. Pryor told The Washington Post in 2007. “He’s a marvelous letter-writer — expressive, lusty, funny, charming.”

Ms. Pryor’s study of Lee was praised as the rare Civil War book that cast new light on a familiar subject.

“She impressively captures Lee’s character and personality,” Yale historian David W. Blight wrote in the Boston Globe, and “judiciously chips away at the marble encasements around the real Lee.”

Among other honors, “Reading the Man” won the 2007 Jefferson Davis Award, presented by Richmond’s Museum of the Confederacy. It also shared the prestigious Lincoln Prize, presented by Pennsylvania’s Gettysburg College and the Gilder Lehrman Institute of American History in New York for the year’s best books on Abraham Lincoln and the Civil War.

“Just before [Lee] died,” Ms. Pryor said in a 2008 interview with Humanities, a publication of the National Endowment for the Humanities, “he told a friend that ‘the great mistake of my life was taking a military education.’ This is a terrible statement: Lee is in essence regretting his entire life.”

Mary Elizabeth Brown was born on March 15, 1951, in Gary, Ind. Her father was an executive with AT&T, and the family moved frequently around the country. Ms. Pryor completed high school in Summit, N.J.

After graduating in 1973 from Northwestern University in Evanston, Ill., she joined the Park Service, where one of her first jobs was operating the elevator at the Washington Monument. She later did historical research on agriculture and architecture.

Ms. Pryor, who had a second bachelor’s degree from the University of London, received a master’s degree in history from the University of Pennsylvania in 1977.

She moved to Richmond from Washington in 2009 and taught in the continuing education program at the University of Richmond. She completed a new book about Lincoln shortly before her death.

Her marriages to Anthony Pryor and Frank Parker ended in divorce. Survivors include her mother, Mary Brown Hamingson of Princeton, N.J.; and two sisters, Beverly Louise Brown of London and Peggy A. Brown of Philadelphia.

Ms. Pryor became interested in Barton when the Park Service acquired her house in Glen Echo in the 1970s.

Besides founding the Red Cross, Barton treated battlefield casualties during the Civil War, championed public education and was an early advocate of voting rights for women and African Americans.

“Emergency preparedness, the idea and the name, came from her,” Ms. Pryor said in 2008. “Even the name ‘first aid’ she made up.”

As much as she enjoyed writing about Lee and the Confederacy, Barton was “probably the more important American,” Ms. Pryor said in 2008.

“Everybody’s life is better every day because of her. And I can’t say the same thing about Robert E. Lee.”

An earlier version of this article misspelled the last name of Elizabeth Brown Pryor’s mother. It is Hamingson, not Harmingson.