Congress proclaimed March as Irish-American Heritage Month in 1991, and the President issues a proclamation commemorating the occasion each year.

Originally a religious holiday to honor St. Patrick, who introduced Christianity to Ireland in the fifth century, St. Patrick’s Day has evolved into a celebration of all things Irish. The world’s first St. Patrick’s Day parade occurred on March 17, 1762, in New York City, featuring Irish soldiers serving in the English military. This parade became an annual event, with President Truman attending in 1948.

Following are some key statistics compiled by the U.S. Census Bureau in honor of St. Patrick's Day.

33.1 million, or 10.4%

Number and percentage of U.S. residents who claimed Irish ancestry in 2014. This number was more than seven times the population of Ireland itself (4.6 million). Irish was the nation’s second-most frequently reported European ancestry, trailing German.

21.5%

Percentage of Massachusetts residents who claimed Irish ancestry in 2014. New Hampshire, at 20.9 percent, is the only other state in which more than 20 percent claimed Irish ancestry. (The rates for the two states were not statistically different from each other.) California had 2.5 million people claiming Irish ancestry, which was the highest of any state. Two other states — New York and Pennsylvania — also had more than 2 million Irish-Americans.

22.8%

Percentage of the Boston metropolitan area population that claimed Irish ancestry, the highest percentage among the 50 most populous metro areas. Boston is home to the Celtics of the National Basketball Association.

20,590

Estimated number of U.S. residents who spoke Irish Gaelic. All except about 2,500 of them also spoke English “very well.”

$34.0 billion

Value of goods imported from Ireland in 2014. This compared with $7.8 billion exported there.

235,701 & 41,582

Number of full-service restaurants and drinking places (bars and taverns), respectively, in the U.S. in 2013. Many people will head to one or the other to celebrate St. Patrick’s Day.

For more key statistics, please visit the U.S. Census Bureau's latest issue of Facts for Features on St. Patrick's Day.