Tradition has kept Peter and Paul together on a single feast since the earliest days of the Roman church. They are the two pillars of the apostolic Church — Peter, the simple fisherman to whom Christ gave the keys; Paul, the educated Pharisee whom Christ struck down on the Damascus road.
Both were martyred at Rome during Nero's persecution. Peter was crucified head-down, by his own request, judging himself unworthy to die as his Lord had. Paul, as a Roman citizen, was beheaded outside the city walls. Their two basilicas — St. Peter's at the Vatican and St. Paul Outside the Walls — mark the places of their burial and remain pilgrimage sites today.