"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 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."
Via Seth Dixon