NEW YORK (AP) — St. Patrick’s Day, the annual celebration of all things Irish, is being marked in cities across the country on Monday with boisterous parades and celebrations. New York City hosts one of the largest and oldest parades in the United States.

President Donald Trump, Vice President JD Vance and Speaker of the House Mike Johnson kicked off the Irish celebrations last week by welcoming ​Taoiseach Micheál Martin to the White House.

Saint Patrick's Day, originally a religious holiday, has blossomed in the United States into a cultural celebration that draws millions. New York and Chicago stand out with their parades and events honoring Irish heritage,

If it’s March, and it’s green, it must be St. Patrick’s Day. The day honoring the patron saint of Ireland is a global celebration of Irish heritage.

Every year thousands of revelers fill the streets in the U.S., Ireland and countries worldwide to celebrate Saint Patrick’s Day, but the real Saint Patrick wasn’t even Irish. NBC News’ Joe Fryer took a deeper look at Saint Patrick’s lasting influence and the history behind the holiday.