Katie Letcher was born on May 12, 1938, in Peking, China, to Elizabeth Marston Letcher, an artist, and John Seymour Letcher, a brigadier general in the United States Marine Corps. She received her B.A. in 1959 from Hollins College, and her M.A. from the Johns Hopkins University, and continued her graduate studies at Vanderbilt University from 1961-1962. She married Royster Lyle, Jr., associate director of the George C. Marshall Research Library and Foundation, in 1963, and has two children, Royster Cochran (1971), and Virginia Letcher (1977). She taught in Baltimore, Maryland from 1960-1961 and from 1962-1963 and served as a member of the English Department at Southern Seminary Junior College in Buena Vista, Virginia from 1963-1987, including a period as chair of the English Department from 1968-1980 and as chair of the liberal arts division from 1971-1973. She has also taught as guest instructor at Washington and Lee University in 1987, as well as at Hollins College as writer-in-residence in 1989, and as guest instructor in 1989-1990 and 1992. She has been an Elder Hostel instructor at Southern Seminary and Mary Baldwin College, from 1984 to the present. She has also been a professional folk singer, appearing in Nashville and in Baltimore.
Lyle has authored a television series Footsteps, and has acted in various plays. She has contributed many articles and reviews to newspapers and magazines, including Newsweek. For several years, she wrote a weekly column of comedy and cookery for the Roanoke Times and World News, and she has written poems and short stories for literary magazines. She loves to travel in Europe, enjoys searching for and identifying mushrooms, is a talented amateur chef, and keeps up to date about archaeology, especially in the Aegean region.