St. Patrick is the patron saint of Ireland. March 17 is celebrated in his honor every year, and by the Irish community worldwide.
St. Patrick was born in Britain around 385 A.D. At the age of 16 he was sold into slavery by Irish raiders and spent six years in captivity. It is during this time that he found religion and upon escaping went to Gaul monastery to study. He became convinced that his purpose was to convert people to Christianity and once a priest he spent 30 years traveling around Ireland establishing monasteries, schools and European culture after the fall of The Roman Empire. He died on March 17, 460 A.D.- a date which has been celebrated as St. Patrick's Day ever since.
Traditionally, this is a religious holiday. But today St. Patrick's Day is more of a festival. In Dublin, Boston and other cities across the globe, celebrations include parades, concerts and fireworks, shows which attracts tens of thousands of people- all wearing green, of course.
According to one legend, St.Patrick used three leafed shamrock to explain the concept of Trinity, (What a very interesting way to explain the Trinity uh?) True or not, shamrock remains one of the most significant symbols visible on St. Patrick's Day.
So, there is the history to St. Patrick's Day.