It is known that St. Patrick was born in Britain to wealthy parents Calphurnius and Conchessa near the end of the fourth century. Calphurnius belonged to a Roman family of high rank and held the position of Christian deacon in Gaul or Britain. Conchessa was a near relative of the great patron of Gaul, St. Martin of Tours.
At the age of sixteen, Patrick was taken prisoner by a group of Irish raiders who were attacking his family's estate. They transported him to Ireland where he spent six years in captivity. During this time, he worked as a shepherd, outdoors and away from people. Lonely and afraid, he turned to his religion for solace, becoming a devout Christian.
After more than six years as a prisoner, Patrick escaped. To do so, Patrick walked nearly 200 miles. After escaping to Britain, he studied in the monastery under St. Germain, bishop of Auxerre. The course of study lasted more than fifteen years. He became aware that his calling was to convert the pagans of Ireland to Christianity. But his superiors instead appointed St. Palladius. However, two years later, Palladius transferred to Scotland. Patrick, having adopted that Christian name earlier, was then appointed as second bishop to Ireland.
Familiar with the Irish language and culture, Patrick chose to incorporate traditional ritual into his lessons of Christianity instead of attempting to eradicate native Irish beliefs. For instance, he used bonfires to celebrate Easter since the Irish were used to honoring their gods with fire. He also superimposed a sun, a powerful Irish symbol, onto the Christian cross to create what is now called a Celtic cross, so that veneration of the symbol would seem more natural to the Irish.
Patrick was quite successful at winning converts. This fact upset the Celtic Druids. He was arrested several times but always escaped. He traveled throughout Ireland, establishing monasteries across the country. He also set up schools and churches, which would aid him in his conversion of the Irish country to Christianity.
His mission in Ireland lasted for thirty years. After that time, Patrick retired to County Down. He is believed to have died on March 17, around 460 AD. St. Patrick's remains were wrapped in the shroud woven by St. Brigid's own hands. Just like his birth date, the year he has passed out is a mystery. Some sources say he died at Saul, Downpatrick, Ireland, 17 March, 493 AD. At least the exact day of his death is known. So, 17th of March has been commemorated as St. Patrick's Day ever since.
The St. Patrick's Day custom came to America in 1737. That was the first year St. Patrick's Day was publicly celebrated in Boston. 25 years later, Irish soldiers serving in the English military marched through New York City during the St. Patrick's Day parade on March 17, 1762.
Today people celebrate the day with parades, wearing of the green, and drinking Guinness.