St. Patrick was a bishop living in the 5th century who is believed to have brought Christianity to Ireland. He is one of the patron saints of Ireland. St. Patrick's Day (his feast day on March 17th) is associated with the celebration of Irish culture, especially abroad.
I learned about St. Patrick's Day: how it is celebrated today, how it is viewed nationally (compared to the U.S. perspective), and a bit of its historical roots. The main event in Dublin is the St. Patrick's Day parade, which runs through the city with a variety of music, performers, and decorated floats. It is quite a busy event! Interestingly, the day is celebrated with greater intensity by tourists than by locals. My friends here appreciate the day off from work and may go out with their friends, but it is not the (sometimes wild) event it is for visitors. Many locals leave the city or avoid the centre entirely for the day.
The Sunday before, I went to an Irish dance performance in a spot in Dublin that is very popular with tourists. There were many events throughout the city in the week leading up to St. Patrick's Day. Even the weekend before, there was a buzz in the city. One of the dancers was a friend of a friend of mine - he and the other dancers were incredible! The city was a bit chaotic the night before!