St. Silvester, born in Rome on a date unknown to us, was ordained by Pope St. Marcellinus during the peace that preceded the persecutions of Diocletian. He was a young priest when those days of terror began, and witnessed the abdication of Diocletian and Maximian, eventually witnessing the triumph of Constantine in the year 312. Two years later, he succeeded St. Miltiades as Bishop of Rome. Later that same year, he sent four legates to represent him at the great Council of the Western Church, held at Aries. He confirmed its decision and imparted them to the Church.
The first Council of Nicaea was assembled during his reign in the year 325, but not being able to assist at it in person on account of his advancing years, he sent his legates, who headed the list of subscribers to its decrees, preceding the Patriarchs of Alexandria and Antioch. During his Pontificate, some of the great churches founded at Rome by Constantine — the Basilica and baptistery of the Lateran, the Basilica of the Sessorian palace (Santa Croce), and St. Peter’s Basilica — were built, as well as several cemeterial churches over the graves of martyrs.
Numerous legends dramatize his life and work, e.g., how he freed Constantine from leprosy by baptism, and how he killed a ferocious dragon that was contaminating the air with his poisonous breath. As the Golden Legend has it:
And for the cruelty of Constantine God sent him such a sickness that he became lazar and measel, and by the counsel of his physicians he got three thousand young children for to have cut their throats, for to have their blood in a bath all hot, and thereby he might be healed of his measelry. […] Now it happened that one night after S. Peter and S. Paul appeared to this Emperor Constantine, saying to him: Because thou hast had horror to shed and spill the blood of innocents, our Lord Jesu Christ hath had pity on thee, and commandeth thee to send unto such a mountain there Silvester is hid with his clerks, and say to him that thou comest for to be baptized of him and thou shalt be healed of thy malady. […] Then S. Silvester preached to him the faith of Jesu Christ, and baptized him; and when he was baptized, a great light descended upon him so that he said that he had seen Jesu Christ, and was healed forthwith of his measelry.
Such legends were meant to portray the effects of baptism and Christianity’s triumph over idolatry (Pius V’s Breviary says that he cleansed Constantine “from the leprosy of misbelief”). For a long time, the feast of St. Sylvester was a holyday of obligation.
St. Sylvester was Pope for twenty-four years and eleven months, ranking no. eight of the ten longest-reigning popes. After he died this date in the year 335, he was buried in the cemetarial church over the Catacomb of St. Priscilla, which he helped to build.