Monsignor John Tracy Ellis is Professorial Lecturer in Church History at the Catholic University of America. The career of this pre-eminent church historian is here traced from his early schooling in Illinois to his graduate studies and teaching posts at the Catholic University of America. He has also taught at the University of San Francisco and has held several visiting professorships both here and abroad. Generations of church historians have studied under him. His publications number in the hundreds, but he is best known for a dozen or so books in the field of American Catholic history. For a half-century now he has served on the editorial board of the Catholic Historical Review, from 1941 to 1963 as its managing editor. By his numerous public addresses, essays, and talks on radio and television, he has become a major interpreter of the American Catholic experience to the nation at large. The story of this long and remarkable career are here told in lively and reflective detail. Co-published with the Catholic University Department of Church History.