(Meredith/CNN) -- Most of us celebrate St. Patrick's Day, even if we aren't Irish. But who exactly was this famous Saint and why do we celebrate his life? Here are a few facts you might not know about one of March's most popular holidays.
Facts you probably already know
Legend has it St. Patrick used the shamrock to explain the concept of the Holy Trinity, by showing an unbeliever the three-leafed plant with one stalk.
Shamrocks are the national flower/emblem of Ireland.
St. Patrick's Day is the feast day of St. Patrick, the patron saint of Ireland.
Corned beef and cabbage is a staple at St. Patrick's Day celebrations.
Who was Saint Patrick?
St. Patrick was a Christian missionary and the Apostle of Ireland.
He was born in 385 AD in Britain, which means he isn't Irish.
Patron saints are chosen to protect the interests of a country, place, group, trade or profession, or activity, and to intercede for them in heaven. St. Patrick is responsible for converting the people of Ireland to Christianity.
At sixteen, he was brought to Ireland as a slave.
He escaped six years later and became a priest.
Following a vision, he returned to Ireland to Christianize the Irish people.
He is credited with having driven the snakes out of Ireland. However, most biologists maintain there never were snakes in Ireland.
He died in 461 AD on March 17.
How does Ireland celebrate?
In Ireland, St. Patrick's Day is a national holiday with banks, stores, and businesses closing for the day.
It has primarily been celebrated as a religious holiday.
How does the U.S celebrate?
The first St. Patrick's Day celebration in the United States was held in Boston in 1737.
According to the US Census, 32.7 million US residents claimed Irish ancestry in 2015. This is more than seven times the population of Ireland (4.6 million).
In the United States, St. Patrick's Day is primarily a secular holiday.
New York City
New York City held its first city-wide celebration on March 17, 1762.
In 2002, 300,000 marchers and three million spectators participated in the St. Patrick's Day Parade, make this parade, honoring the heroes and victims of 9/11, the largest parade to date.
In 2011, the 250th New York City St. Patrick's Day Parade is held.
In 2014, the organizers of the New York City St. Patrick's Day Parade announce the first ever LGBT group to march in 2015 under their banner. It represents an end to a ban on openly gay groups in the parade.
Each year, the St. Patrick's Day Parade is held on March 17, unless March 17 falls on a Sunday. When this happens, the parade is held on Saturday the 16th.
The parade marches up 5th Avenue, from 44th to 79th streets. It is often called the world's largest St. Patrick's Day parade.
Chicago held its first St. Patrick's Day parade on March 12, 1955.
If the 17th falls on a weekday, the parade is held the Saturday before.
The Chicago River is dyed green, with a secret recipe, and the parade begins at noon at the corner of Balbo and Columbus Drive.