Henry Mayer, 59, a historian and critic who was the author of highly acclaimed biographies of such champions of American freedom as William Lloyd Garrison and Patrick Henry, died of a heart attack July 24 while bicycling through Glacier National Park in Montana. He lived in Berkeley, Calif.

Mr. Mayer's Garrison biography, "All on Fire: William Lloyd Garrison and the Abolition of American Slavery," was published in 1998 by St. Martin's Press to admiring reviews.

The saga of the publisher and agitator was a finalist for the 1998 National Book Award and winner of the J. Anthony Lukas Book Prize and the Boston Book Review REA Prize for nonfiction. It also was named a New York Times Notable Book of 1998.

The Washington Post, in its review of the book by Michael R. Winston, pointed out that "Most professional historians once disparaged William Lloyd Garrison as a crank and fanatic, but Henry Mayer has finally delineated his heroic role in American history fairly and wholeheartedly in this monumental work of historical biography."

His book on the legendary Virginia lawyer-orator Patrick Henry, "A Son of Thunder: Patrick Henry and the American Republic," was published in 1986 by the University Press of Virginia.

Like his later book on Garrison, the Henry book was hailed by critics for taking a seemingly one-dimensional character and fleshing the life out to the story of a truly remarkable and surprisingly complex individual. His biographies displayed a clear, refreshing, and altogether original view of both two American patriots and American history as well. His books were based on research every bit as rigorous as that displayed by many of today's professional historians, whose impressive academic credentials, endless footnotes, and turgid writing often disguise a lack of originality.

Mr. Mayer, who was not affiliated with a college or university, wrote readable books for a serious audience but without much of the academic baggage that is found in much contemporary biography of historical figures.

He had lived in the San Francisco Bay area since 1971, serving for a time as history and English teacher, and acting director of a private secondary school. He had been a full-time writer since 1980, writing book reviews and essays in addition to works on American history. He had contributed book reviews to such publications as The Washington Post, the New York Times and the San Francisco Chronicle.

In addition to his two biographies, he had been the co-author of two other books, "The Culture of the University: Education and Governance," which was published in 1968, and "As It Happened: A History of the United States," which appeared in 1975. At the time of his death, Mr. Mayer was writing a biography of photographer Dorothea Lange.

Mr. Mayer was born in New York and raised in North Carolina. He graduated from the University of North Carolina in 1963 with highest honors and received a master's degree from the University of California at Berkeley in 1965.

Before settling in the bay area, he taught history at Franklin and Marshall College in Pennsylvania, where he was a critic of U.S. involvement in the Vietnam War.

Mr. Mayer was a member of the American Civil Liberties Union and the National Book Critics Circle. He had done volunteer work in the public schools in Berkeley. His hobbies included cycling and gardening.

Survivors include his wife of 23 years, Dr. Elizabeth T. Anderson, and two children, all of Berkeley; his mother; and a brother.