Sylvester ascended the throne of Peter eleven months after Constantine's Edict of Milan (313) had ended the persecution of the Church. His pontificate of nearly twenty-two years is one of the longest of the early papacy and one of the most consequential — although the early sources for it are thin, much obscured by later legend.
Under his reign the great Roman churches that still anchor the Christian topography of the city were built by imperial patronage: the Lateran Basilica (the cathedral of Rome, dedicated November 9, 324, the 'mother and head of all churches'), Old St. Peter's, and Holy Cross in Jerusalem. The First Council of Nicaea met in 325 — though Sylvester himself was represented by legates rather than presiding in person — and produced the Nicene Creed.
Medieval tradition surrounded him with luxuriant legends: the Donation of Constantine (a 9th-century forgery) purported to make him the recipient of Constantine's transfer of Western imperial authority; the Acta Silvestri described him baptising the emperor on a sickbed (modern scholarship locates Constantine's deathbed baptism much later, by Eusebius of Nicomedia). Sylvester himself remains a quiet figure behind these stories — the bishop in whose see a persecuted Church became, in less than fifteen years, the imperial Church.