Enjoy these numbers along with your celebratory corned beef and cabbage, soda bread and green beer:

30.5 million US residents claim Irish ancestry, the second most frequently reported ancestry, according to the Census Bureau's Ancestry 2000 report.

4.5 million Irish immigrants traveled to the United States between 1820 and
1930.

4.2 million, roughly, is the population of Ireland.

248 is the number of consecutive years New York City has put on its St. Patrick’s Day parade.

100 pounds of green dye were added to the Chicago River St. Patrick’s Day, 1962. The river was green for a week. (See the 2009 dyeing in this video.)

24 percent of Massachusetts residents have Irish ancestry, says the Census Bureau.
 
9 cities or towns in the United States are named Dublin (also from the Census Bureau).

0 is the number of snake species native to Ireland (which has more to do with geography than St. Patrick, if you ask the National Zoo).

And you'll find innumerable tips and resources for tracing your Irish roots in our Irish genealogy research toolkit.