Michael O'Brien was born in Green Bay, Wisconsin, and studied at the University of Notre Dame and the University of Wisconsin at Madison, where he received a Ph.D. in history. He is the author of the widely praised John F. Kennedy: A Biography, a full-scale study based on eleven years' research into letters, diaries, financial papers, medical records, manuscripts, and oral histories; and a concise analytical life of the president, Rethinking Kennedy. He is now emeritus professor of history at the University of Wisconsin, Fox Valley, and lives in Door County, Wisconsin.