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 S 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.

The number of U.S. residents who claimed Irish ancestry in 2010 was 34.7 million. This number was more than seven times the population of Ireland (4.58 million). Irish was the nation’s second most frequently reported ancestry, trailing German.

Thirteen percent of New York state residents said they were of Irish ancestry in 2010. This compares with a rate of 11.2 percent for the nation as a whole.

Seven places in the United States are named Shamrock, the floral emblem of Ireland; Mount Gay-Shamrock, W.Va., Shamrock, Texas, Shamrock Lakes, Ind., Shamrock, Okla., and Shamrock Township in Minnesota, Nebraska and Missouri.

Sixteen cities in the United States share the name of Ireland’s capital, Dublin. The most populous of these is in California with a population of 46,036.