I took bits & pieces of interesting information From Wiki:
Saint Patrick (386–March 17, 493 AD, see below) is primarily known as the patron saint of Ireland (along with Saint Brigid and Saint Columba). He is also the patron saint of Nigeria, which was evangelized primarily by Irish missionaries, especially priests from Saint Patrick's Missionary Society.
Although he came from a Christian family, he was not particularly religious before his capture. However, Patrick's enslavement markedly strengthened his faith. It was at this time he learned the native Celtic language and the customs of the druids, as his master was a druidic high priest. He escaped at the age of twenty-two, as legend has it, under the direction of an angel, and spent twelve years in a monastery in Auxerre, where he adopted the name Patrick (Patricius, in Old Irish spelled Pádraig). One night he heard voices begging him to return to Ireland, and he thus, by now in his thirties, became one of the first Christian missionaries in Ireland, being preceded by Palladius (died c.457/461).
While Patrick encouraged the Irish to become monks and nuns, it is not certain that he was a monk himself. It is even less likely that in his time the monastery became the principal unit of the Irish Church, although it was in later periods.
One famous story relates that at the annual vernal fire that was to be lit by the High King at Tara, when all the fires were extinguished so they could be renewed from the sacred fire from Tara, Patrick lit a rival, miraculously inextinguishable Christian bonfire on the hill of Slane at the opposite end of the valley.
Pious legend credits Patrick with banishing snakes from the island, though post-glacial Ireland never actually had snakes; one suggestion is that snakes referred to the serpent symbolism of the Druids of that time and place, as shown for instance on coins minted in Gaul (see Carnutes), or that it could have referred to beliefs such as Pelagianism, symbolized as "serpents."
According to tradition, St. Patrick fasted on Croagh Patrick for forty days and forty nights... It is said that at the end of Saint Patrick's 40-day fast, he threw a bell down the side of the mountain, banishing all the snakes and serpents of Ireland. The place where the bell is said to have landed, and where the snakes are said to be banished to is in reality the U-shaped valley created by a glacier flowing into Clew Bay in the last Ice Age.
On 'Reek Sunday', the last Sunday in July every year, over 25,000 pilgrims climb the mountain, many of whom climb barefoot.
Legend also credits Patrick with teaching the Irish about the concept of the Trinity by showing people the shamrock, a three-leaved clover, using it to highlight the Christian dogma of 'three divine persons in the one God' (as opposed to the Arian belief that was popular in Patrick's time). However, this appears to be an 18th century fabrication.
Decades of contention eventually ended with most historians now asserting that Patrick was indeed most likely to have been active in the mid-to-late 5th century.
The compiler of the Annals of Ulster stated that in the year 553:
"I have found this in the Book of Cuanu: The relics of Patrick were placed sixty years after his death in a shrine by Colum Cille. Three splendid halidoms were found in the burial-place: his goblet, the Angel's Gospel, and the Bell of the Testament. This is how the angel distributed the halidoms: the goblet to Dún, the Bell of the Testament to Ard Macha, and the Angel's Gospel to Colum Cille himself. The reason it is called the Angel's Gospel is that Colum Cille received it from the hand of the angel."
The placement of this event under the year 553 would certainly seem to place Patrick's death in 493, or at least in the early years of that decade.
How this became the green-loving, beer-drinking, food-coloring dying & glitter laden frivolity of the American rendition of this holiday that it is today, is beyond me: but, I like to see people happy: and I think it's been a great evolution: just everyone please get a designated driver! Thanks & Enjoy the festivities & green, well, everything! ~Alli