The history of St. Patrick’s Day dates back more than 1,000 years.

Although largely a secular holiday today, St. Patrick’s Day originated as a religious holiday. Christians in Ireland began observing a feast day for St. Patrick around the ninth and 10th centuries. On the holiday, which falls during the Christian season of Lent, Irish families traditionally attended church in the morning and celebrated in the afternoon. Lenten prohibitions against the consumption of meat were waived, and people danced, drank, and feasted on the customary meal of Irish bacon and cabbage.

Starting in the 17th century, settlers in America established new holiday traditions. St. Patrick’s Day parades and feasting on corned beef and cabbage were American—not Irish—creations. Even so, people around the world continue to participate in parades, eat, drink, and wear green on the holiday—all in the name of celebrating Irish culture.

St. Patrick, who lived during the fifth century, is the patron saint of Ireland and its national apostle. Born in Roman Britain, he was kidnapped and brought to Ireland as a slave at age 16. He later escaped but returned to Ireland and is credited with spreading Christianity among its people.

In the centuries following Patrick’s death (believed to have been on March 17, 461), the mythology surrounding his life became ever more ingrained in Irish culture.

Perhaps the most well-known legend of St. Patrick is that he explained Christianity’s Holy Trinity—the Father, Son and Holy Spirit—using the three leaves of a native Irish clover, the shamrock.