The beginning of the Gospel of Jesus Christ, the Son of God…
The time is fulfilled, and the kingdom of God is at hand. Repent, and believe in the Gospel.
Saint Mark was a missionary companion of Saint Peter and Saint Paul (1 Peter 5:13; Acts 12:12-17,25).
As Saint Peter’s likely scribe, Mark’s Gospel can be referred to as the Memoirs of Saint Peter. Saint Mark presents the disciple’s mission through the person and event of Jesus Christ in a brief narrative of his ministry, passion, death, and resurrection. According to Mark, the Christian disciple’s mission is to proclaim the ‘the good tidings,’ a change of heart, to purge the impure spirits of fear, obduracy, and worldly possessiveness, and thereby to enter as a child in faith into the kingdom of God (Mark 6:7-12).
Saint Mark proclaimed the Christian faith in Alexandria, founding the Church there. He was martyred there by pagans, hanged and dragged through the streets.

Later, his remains were stolen by Venetian merchants, to be housed in the basilica of San Marco in Venice. Venice then adopted Saint Mark’s symbol of the Lion as the symbol of their city.

From the Collect prayer of the Feast Day:
O God, who raised up Saint Mark, your Evangelist, and endowed him with the grace to preach the Gospel, grant, we pray, that we may so profit from his teaching as to follow faithfully in the footsteps of Christ.