A secret map of Ireland's coastline played a crucial role in taking down a powerful alliance of pirates that had based itself in the southwest of Ireland in the 17th century.

Almost 1 in 10 Americans claim Irish heritage, according to the Census Bureau. But even the non-Irish celebrate Saint Patrick's Day.

Though only 1 in 9 people in the U.S. claim Irish heritage, about 61% of Americans plan to celebrate Saint Patrick's Day, according to the National Retail Federation. Wearing green, hosting a ...