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 for 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 Harry Truman attending in 1948. Congress proclaimed March as Irish-American Heritage Month in 1995, and the president issues a proclamation commemorating the occasion each year.

Here are some statistics about the Irish in America as provided by the Census Bureau:

• 34.5 million - Number of U.S. residents who claimed Irish ancestry in 2011. This number was more than seven times the population of Ireland itself (4.68 million). Irish was the nation’s second most frequently reported ancestry, trailing only German.