The United States was founded mostly by Protestants and remained overwhelmingly Protestant for many decades, a fact Protestants did not want Roman Catholics to forget. When Catholics began arriving here in large numbers in the middle of the 19th century, they found that in public schools the majority religion was pervasive and inhospitable.

Catholic children, one historian wrote, had “to attend schools where the King James Bible was read, where Protestant hymns were being sung” and where lessons were “very much anti-Catholic.” Catholics resisted, and Protestants took offense. In Philadelphia, the conflict provoked deadly riots and the torching of a Catholic church.