In Chicago, the river runs green on St. Patrick’s Day. In New York City, Fifth Avenue becomes a rolling sea of green as upwards of 2 million spectators line the 1.5-mile parade route. And in Boston, where “Southie” remains synonymous with all things Irish despite a changing demographic, the annual “wearing of the green” is an almost sacred tradition.

The often-raucous St. Patrick’s Day festivities we celebrate across the United States today evolved from more staid observances initiated by 18th-century settlers of Irish descent. Established in Boston in 1737, the Charitable Irish Society led the way with a fundraising initiative to aid Irish immigrants, marking the day with a worship service. Similar Irish efforts, rooted in charitable work, worship and honoring the homeland, created more widespread observances centered on March 17.

These subdued rituals more closely aligned with traditions in Ireland, where St. Patrick’s Day was — and is — a holy day of obligation. In fact, until the 1970s, pubs in Ireland remained closed on St. Patrick’s Day; and it was just two decades ago, in 1995, that the government of Ireland established the official St. Patrick’s Festival in Dublin. The initiative, conceived to showcase Irish culture worldwide, has grown from its inaugural one-day event on March 17, 1996, to a five-day extravaganza set for March 13–17 in 2015.

The 2015 St. Patrick’s Festival marks the second of a three-year theme, “Past, Present and Future,” tracing the history of Irish culture through the ages. In 2014, the parade theme drew on Ireland’s past for inspiration, fielding pageants based on Irish folklore. The 2015 theme, “Present,” will showcase today’s Ireland, while 2016 will center on expectations for the Emerald Isle’s next hundred years.

The annual St. Patrick’s Day parade brings more than half a million revelers to Dublin, but the myriad festivities surrounding the ritual march also draw major crowds from around Ireland and around the world. The roster of events includes music and dance, street theater, fireworks, exhibitions, walking tours, craft beer and food markets — in general, a celebration of all things Irish.

And while Dublin may be the epicenter of Ireland’s St. Patrick’s Day celebrations, annual festivities take place throughout the country, with major events slated for Cork, Galway, Killarney, Kiltimagh, Limerick and Sligo, as well as Armagh, Belfast, Downpatrick and Holywood in Northern Ireland.

Come one. Come all. Céad míle fáilte! A hundred thousand welcomes!