Marcus F. Cunliffe, 68, a professor of American history at George Washington University who was a noted author and witty and incisive commentator on this country's history and literature, died Sept. 2 at George Washington University Hospital. He had leukemia.

Mr. Cunliffe, a resident of Washington, had served on the George Washington University faculty since 1980.

He was the author of books that included both the popular and penetrating biography "George Washington: Man and Monument," published in 1958, and "The Literature of the United States," published in 1954 by Penguin books in Britain.

In 1954, Mr. Cunliffe was a young, relatively unknown lecturer in American studies at Manchester University in England. The book became a standard text on the subject and received glowing reviews in Britain's most prestigious journals.

The book was the beginning of his enviable reputation as a writer, teacher, and something of a father of interdisciplinary American studies in his native Britain.

His writing and research resulted in books that were both scholarly and written with a rare and elegant style. His interests ranged intellectual horizons and his works were not contained by the narrow boundaries of academic disciplines.

In addition to his research, he also maintained a lively interest in the work and lives of former students and colleagues. Some colleagues remember him shunning administrative duties, office politics and academic bookkeeping chores. He once claimed in a "Who's Who" entry that his "recreations" included "the pursuit of happiness" and "filling in questionnaires."

He wrote on the American presidency and slavery, and books for children. His 1968 book "Soldiers and Civilians: The Martial Spirit in America, 1775-1865" examined our society and military. He also was co-editor of "Pastmasters: Some Essays on American Historians," published by Harper in 1969. In additon to his books and scholarly works, he contributed to such publications as The Washington Post's Book World.

It may have been the mythical, historical and historic figure of George Washington that most intrigued him. In addition to his noted one-volume study, he was co-author of a juvenile work about the country's first president. In 1962, he edited for Harvard University Press a new edition of the classic "Life of Washington" by M.L. Weems.

In a 1981 interview with The Post, he spoke of how elusive Washington could be as a historical figure, pointing out that while the speeches and writings of Jefferson and Lincoln have become something of a sacred text to Americans, Washington is more important as a symbol. He also pointed out that this city's famed monuments to Lincoln and Jefferson contain lifelike statues of the presidents, but Washington's monument is an abstract representation.

Mr. Cunliffe was an intelligence officer in the British army's Royal Tank Regiment during World War II. A graduate of Oxford University's Oriel College, he studied as a Commonwealth Fund Fellow at Yale University from 1947 to 1949.

He taught at Manchester from 1949 to 1965, then at the University of Sussex until 1980. During those years, he also spent time as a visiting professor at Harvard and Stanford universities, as well as the University of Michigan. He was a fellow at the Woodrow Wilson International Center in Washington in 1977 and 1978.

He said he became interested in America from seeing American films as a child, reading the works of Stephen Crane and James Thurber in school and watching Americans fight during World War II. After the war, as he pursued American studies and the British Empire began to wane, others in Britain became equally fascinated with our new power and history.

His marriages to Mitzi Solomon and Lesley Hume ended in divorce.

Survivors include his wife, Phyllis Palmer of Washington; three children by his first marriage, Antonia Cunliffe Davis of Birmingham, England, and Jason and Shay Cunliffe, both of New York City; and four grandchildren.