Pope Pius IV issued a Papal bull confirming the decrees of the Council of Trent that defined Catholic doctrine in the face of the Protestant Reformation.

Pope Julius II laid the cornerstone of the current St. Peter’s Basilica, one of Catholicism’s most sacred buildings.

Born Giovanni Maria Mastai-Ferretti, Pius IX’s election by the Papal conclave of 1846 came at a time of significant political unrest across Europe.