A son of Lewis A. Lapham and his wife, the former Jane Foster, Lapham was born and grew up in San Francisco. His grandfather Roger Lapham was mayor of San Francisco, and his great grandfather Lewis Lapham was a founder of Texaco. Through his grandfather, Lapham is a first cousin once removed of actor Christopher Lloyd.

Lapham was educated at the Hotchkiss School, Yale University, where he joined the literary society St. Anthony Hall, and Magdalene College, Cambridge.

In 1972, Lapham married Joan Brooke Reeves, the daughter of Edward J. Reeves, a stockbroker and grocery heir, and Elizabeth M. Brooke (formerly the wife of Thomas Wilton Phipps, a nephew of Nancy Astor). They have three children:

• Delphina (married Prince Don Bante Maria Boncompagni-Ludovisi)
• Andrew (married Caroline Mulroney, a daughter of former Canadian Prime Minister Brian Mulroney)
• Winston

Lewis Lapham served as editor of Harper's Magazine from 1976 to 2006 (with a hiatus from 1981 to 1983). He was managing editor from 1971 to 1975, after having worked for the San Francisco Examiner and New York Herald Tribune. He is largely responsible for the modern look and prominence of the magazine, having introduced many of its signature features including its famed Harper's Index. He announced that he would become editor emeritus in Spring 2006, continuing to write his Notebook column for the magazine as well as editing a new journal about history, Lapham's Quarterly. Lapham has also worked with the PEN American Center, sitting on the board of judges for the PEN/Newman's Own Award. This February, he will be inducted into the American Society of Magazine Editors' Hall of Fame.

• Fortune's Child 1980; ISBN 0-385-14887-9
• Money and Class in America 1988; ISBN 1-55584-109-0
• Imperial Masquerade 1990; ISBN 1-55584-449-9 (hardcover); ISBN 0-517-11018-0
• The Wish for Kings: Democracy at Bay 1993; ISBN 0-8021-1446-6
• Hotel America 1995; ISBN 1-85984-952-0 (hardcover); ISBN 1-85984-062-0 (paperback)
• Waiting for the Barbarians 1997; ISBN 1-85984-882-6
• Lapham's Rules of Influence 1999; ISBN 0-679-42605-1
• The Agony of Mammon 1999; ISBN 1-85984-710-2
• Lights, Camera, Democracy! 2001; ISBN 0-679-64713-9; ISBN 0-8129-9162-1
• Theater of War 2003; ISBN 1-56584-772-5 (hardcover); ISBN 1-56584-847-0 (paperback)
• 30 Satires (a collection of essays) 2003; ISBN 1-56584-846-2
• Gag Rule 2004; ISBN 1-59420-017-3
• With the Beatles 2005; (Melville House Publishing); ISBN 978-0-976658-32-0
• Pretensions to Empire: Notes on the Criminal Folly of the Bush Administration, by Lewis H. Lapham (The New Press: 2006), 288 pages; ISBN 1-59558-112-X

His writing has appeared in Life, Commentary, Vanity Fair, National Review, Yale Literary Magazine, ELLE, Fortune, Forbes, American Spectator, The New York Times, The Walrus, Maclean's, The Observer (London), and the Wall Street Journal. Lapham also served as a judge for the PEN/Newman's Own First Amendment Award.

Lapham is the host and author of the PBS series, America's Century, and he was host of the weekly PBS series, Bookmark.

Lapham is currently the host of The World in Time: radio discussions with scholars and historians on Bloomberg Radio that open the doors of history behind the events in the news. Podcasts of the weekly talks are available at Bloomberg.com .

Lapham wrote The American Ruling Class (2005), a movie done in documentary style and featuring fictional characters and real people, i.e. Bill Bradley, Hodding Carter III and Barbara Ehrenreich, author of Nickel and Dimed, pondering the question "is there a ruling class in America?" Lapham states at the movie's conclusion that "if you're not in, you're out." The movie aired on the Sundance Channel, July 30, 2007.