From the colonial era, through the beginning of the 20th century, Catholics had difficulty finding a place in America’s overwhelmingly Protestant culture. Yet, as the stressors of the “New Immigration” and WWI led to the nativist response called "100% Americanism," hostility against Catholics intensified. At the same time, one of the principles that nativists celebrated with greatest exuberance was America’s tradition of religious freedom. How could anti-Catholic secularists think that they were actually protecting religious freedom by excluding Catholics from the public square? My thesis is that advocates of "100% Americanism,” like their Protestant forbearers, based the boundaries of the public square on an individualistic epistemology, such that their religious beliefs were welcomed and encouraged but Catholic beliefs were excluded.