Celebrated annually on March 17th, St. Patrick’s Day is a holiday known for parades, shamrocks, and all things Irish. 

“The celebration of St Patrick’s Day has long been an important date in the Irish folk calendar,” explained Clodagh Doyle, Keeper of the Irish Folklife Division at the National Museum of Ireland. 

“The traditions observed today have been noted over the centuries and evidence for these can be found in our early Irish literature and our folklore. Some of these folk customs developed over time into the St Patrick's Day festival we recognize today."

St. Patrick is credited with bringing Christianity to Ireland, and one of his most famous symbols is the shamrock. The widely held belief that St. Patrick used the shamrock to explain the concept of the Holy Trinity is a relatively late one. It is unlikely that the Irish needed an explanation of the concept of three persons in one, as triads were central to pre-Christian Celtic religious traditions. 

Thomas Dinely, an Englishman traveling through Ireland in 1681, noted that people of all distinctions wore crosses and green shamrocks to commemorate the saint on this day. 

Who Was St. Patrick and the History Behind Saint Patrick's Day | Drive Thru History Special

A history of St Patrick's Day traditions and customs | National Museum of Ireland