In a few days, Americans all across the country will pin up their shamrocks, clothe themselves in green, and raise a Guinness or two to St. Patrick, patron saint of Ireland. Most of them have never set foot on the Emerald Isle. Many more haven’t even a drop of Irish blood in their bodies. And yet, it won’t stop them from celebrating with all things green.

Why has St. Patrick’s Day become such a big deal in a country thousands of miles across the Atlantic from where it was born? And where did it all start in the first place?

St. Patrick, namesake to the day and national apostle of Ireland, wasn’t even Irish. He was a Roman citizen, born in modern-day Britain during the fifth century, when the country was still a part of the Roman empire. His father was a Christian deacon which, in those days, meant tax incentives and wealth, so it’s no surprise the family was subject to raids and attacks from their less fortunate countrymen. During one such raid, at the age of sixteen, Patrick was taken captive and sent to Ireland to work as a slave. Alone and afraid, he turned to his religion and, despite being raised in a ‘church’ household, it was only then that Patrick became a devout Christian.

After more than six years in captivity, Patrick finally escaped, doing so, he claimed, because he was ordered by God in a dream. Returning to Britain, he began a fifteen year course of religious training, believing it was God’s will for him to return to Ireland to spread the news of the gospel. Although legend says that it was St. Patrick who introduced Christianity to Ireland, there were, in fact, already many Christians in the land and, upon his return, St. Patrick began to minister to them. Converting pagans to Christianity was the second, and lesser, part of his mission.

Because Irish culture during this time relied heavily on oral legends, St. Patrick’s life after his return to Ireland is so heavily entwined with tradition and myths, its hard to separate the two. Did St. Patrick really drive all the snakes out of Ireland after they attacked him during an attempted 40-day fast? More than likely not, as fossil records have suggested snakes never lived on the Emerald Isle in the first place. Did his walking stick, thrust into the ground during a particularly passionate sermon, take root and grow into a living tree? Even more unlikely. Did he really baptize hundreds of people in a single day? Perhaps, though it sounds exhausting.

But, fantastical stories or not, St. Patrick’s success and legacy in changing the religious landscape of Ireland is undeniable. Rather than attempt to eradicate traditional Irish beliefs, at the risk of alienating his intended audience, Patrick chose to incorporate them into his message, The sun was a powerful Irish symbol; Patrick added it to the Christian cross, creating the symbol we now know as the “celtic cross.” He added the tradition of bonfires to Easters, since the pagans were used to honoring their gods with fire. And, perhaps most famously, he used the three leaves of the Irish clove to explain the Holy Trinity.

St. Patrick died on March 17, 461 in Saul, where he’d built his first church. Since then, the Irish have commemorated the day with a religious feast, attending church in the morning and, since it took place during the Christian season of Lent, holding a somber, respectful celebration in the afternoon. However, the rules against meat were waived for one day, and people were allowed to feast on Irish staples of bacon and cabbage. In 1631, the religious importance of the day was sealed when it was recognized  by the Vatican.

St. Patrick’s day as we know it, however, began not in Ireland, but in the United States. The first parade to honor St. Patrick was held in New York in 1766, when a group of Irish Catholic members of the British army marched through the streets in honor of the “Irish saint.”

Through the years, as the number of Irish immigrants increased, so did the prejudices against them. Discriminated against and unfairly labeled as violent drunkards, offended Irish-Americans viewed the day as a chance to showcase their civic pride and cling to old traditions in a strange and unwelcoming new land. Because of this, early St. Patrick’s Day celebrations were held only in heavily Irish neighborhoods, although the appeal soon grew, sweeping into cities and becoming a day celebrated by millions of Americans across the country, many without a single drop of Irish blood. But…why?

Perhaps its because it’s a day symbolizing the “hybrid” nature of most Americans–identifying with “somewhere else” along with your American-ness. In a land full of migrants, St. Patrick’s Day has become a day in which we celebrate our “other-ness,” regardless of where that “other-ness” lies. In a sense, St. Patrick’s Day has morphed into a celebration of immigrants. And, no matter how many generations pass, we are all immigrants.

And, on one day at least, we’re all Irish too.