In America, St. Patrick’s Day, on March 17, has long been commemorated with rollicking festivities, but until recent decades, the holiday, which honors Ireland’s patron saint, was traditionally a more solemn occasion on the Emerald Isle.

The man for whom St. Patrick’s Day is named was born into an aristocratic family in Roman Britain around the end of the fourth century. As a teenager, he was kidnapped by Irish pirates and taken to Ireland, where he was held as a slave for a number of years. He eventually escaped the island, only to return later as a missionary and convert part of the population to Christianity. Centuries after his death, which some sources cite as March 17, 461, although the exact date is unknown, Patrick became the patron saint of Ireland, and March 17 became a holy day of obligation for the nation’s Catholics.

Thanks to Irish immigrants in the United States and elsewhere, St. Patrick’s Day evolved from a religious holiday into a secular celebration of all things Irish. The first St. Patrick’s Day parade was held in New York City in the 1760s, by Irishmen serving there in the British military. During the 19th century, when Irish Catholic immigrants faced discrimination in Protestant-majority America, St. Patrick’s Day parades became an opportunity to show strength in numbers. 

Today, with some 35 million Americans claiming to be primarily or partially of Irish descent—making Irish ancestry the second-most commonly reported in the United States, after German—the wearing of the green on March 17 is still going strong. (Australia and Canada are among other locales with long-standing St. Paddy’s Day traditions.)

Meanwhile, back in the old country, where until the 1970s pubs were closed on St. Patrick’s Day, the Irish are catching up to their counterparts across the pond when it comes to revelry. Since the mid-1990s, the government, in part to promote tourism and boost the economy, has sponsored a multi-day St. Patrick’s Festival in Dublin, featuring a parade and a variety of performances and activities; there are similar events in other sections of the country as well.