The article below can be found at About.com
St. Patrick and the Snakes of Ireland:
St. Patrick is known as a symbol of Ireland, particularly around every March. One of the reasons he’s so famous is because he supposedly drove the snakes out of Ireland, and was even credited with a miracle for this. What many people don’t realize is that the serpent was actually a metaphor for the early non-Christian faiths of Ireland. It’s important to note that he did not physically drive the “Snakes” from Ireland, but instead St. Patrick brought Christianity to the Emerald Isle. He did such a good job of it that he began the conversion of the entire country to the new religious beliefs, thus paving the way for the elimination of the old systems. While it’s true that snakes are hard to find in Ireland, this may well be due to the fact that it’s an island, and so snakes aren’t exactly migrating there in packs.
The real St. Patrick was believed by historians to have been born around 370 c.e., probably in Wales or Scotland. Most likely, his birth name was Maewyn, and he was probably the son of a Roman Briton named Calpurnius. As a teen, Maewyn was captured during a raid and sold to an Irish landowner as a slave. During his time in Ireland, where he worked as a shepherd, Maewyn began to have religious visions and dreams — including one in which showed him how to escape captivity. Once back in Britain, Maewyn moved on to France, where he studied in a monastery. Eventually, he returned to Ireland to “care and labour for the salvation of others”, according to The Confession of St. Patrick, and changed his name to Patrick, which means “father of the people.”
Today, St. Patrick’s Day is celebrated in many places on March 17, typically with a parade (an oddly American invention) and lots of other festivities. However, some modern “Snakes” refuse to observe a day which honors the elimination of old beliefs in favor of new. It’s not uncommon to see non-Christians wearing some sort of snake symbol on St. Patrick’s Day, instead of those green “Kiss Me I’m Irish” badges.