November 18th, the Memorial of the Dedication of the basilicas of St. Peter and of St. Paul, is a feast dedication that likely dates to the 11th century. Both of the churches, built to mark the burial places and typical of the 4th-century basilica type, have since been renovated or reconstructed. Each also became associated with imperial patronage very early in their building histories. For example, Prudentius records the involvement of Emperor Honorius in the completion and dedication of San Paolo fuori le Mura.
Saint Peter’s Basilica was not only an imperial foundation but also a place of assistance to the poor, a pilgrimage destination, and a structure central to the ceremonial life of the city. According to Ambrose, by the papacy of Pope Liberius (352-66) mass was being celebrated in St. Peter’s even though, at that time, the Feast Day of Saint Peter and Paul was still being celebrated in the catacombs. This was soon to change, however; by the end of the 4th century, the June 29th celebrations began at St Peter’s basilica and concluded at San Paolo fuori le Mura.
References: McKitterick, Rosamond, John Osborne, Carol M. Richardson and Joanna Story Eds. Old Saint Peter’s, Rome. Cambridge: Cambridge University Press, 2013; “S Paolo fuori le Mura (Rome),” Gorve Art Online. Oxford Art Online.
Bernhold Werner, San Paolo fuori le Mura, Rome, Italy. Photo credit: Wikipedia Commons.
Interior, San Paolo fuori le Mura, 4th century. Rome, Italy. Photo credit:Wikipedia Commons.
Saint Peter’s, Rome, Italy. Photo credit: Jennifer D. Webb
Further reading: Roberta Vicchi. The Major Basilicas of Rome: Saint Peter’s, San Giovanni in Laterano, San Paolo fuori le Mura, Santa Maria Maggiore. London & New York: Scala Group, 1999; Peter Brown. The Cult of the Saints: Its Rise and Function in Latin Christianity. Chicago: University of Chicago Press, 2014.