St. Patrick was born in Roman Britain, around 389. When he was 16, he was sold into slavery to Ireland where he was a shepherd for 6 years. While in captivity he studied and turned to religion. He wrote :
"The love of God and his fear grew in me more and more, as did the faith, and my soul was rosed, so that, in a single day, I have said as many as a hundred prayers and in the night, nearly the same."
"I prayed in the woods and on the mountain, even before dawn. I felt no hurt from the snow or ice or rain."
He had another dream in which the people of Ireland were calling out to him "We beg you, holy youth, to come and walk among us once more."
He escaped slavery and later returned to Ireland as a missionary, determined to convert Ireland to Christianity. He used the shamrock to explain the Holy Trinity.
He was ordained as Bishop of Ireland in 431 (by St. Germanus). He was able to secure tolerance for Christians in Ireland during his life there. He is said to have died in 461 and to be buried in Downpatrick (the first church). St. Patrick's Cathedral in Dublin was built in the 12th Century. He is also said to have drummed the snakes from Ireland and into the sea.