Gordon C. Zahn (1918–2007) was a Catholic sociologist and pacifist whose research was shaped by and helped shape post-World War II Catholicism in the United States. For when Zahn’s most well-known book, In Solitary Witness: the Life and Death of Franz Jägerstätter, was published in 1964, it was generally believed that Catholics could not be conscientious objectors. By the time Jägerstätter (an Austrian Catholic martyred for refusing to fight in Hitler’s army) was beatified in 2007, a very real shift had taken place within Catholic thinking as pacifism moved much closer to the center. Zahn played no small role in that shift. In this article I will address the significance of Gordon Zahn’s life and work by first sketching out his story and then by looking at the post-war U.S. Catholicism, which Zahn’s work challenged—and how this milieu shaped the way Zahn’s research has been portrayed. Finally, I will suggest some of the ways Zahn was and continues to be an important figure, representing something of a “counter-tradition” in thinking about the relationship between Catholicism and the United States.