On St. Patrick's Day, everyone's Irish. Year-round, about 32 million Americans, or nearly one-tenth of our nation's people, can fully or partially claim that heritage. While many immigrant groups came to the U.S. due to hardship, the first great surge of Irish immigration was literally to avoid starvation during the Great Irish Famine of 1845-52. Many stayed, built new lives, raised families and were later joined by others. Along the way, they helped to build cities, transform small towns, and, yes, host some great St. Patrick's Day Parades.

The most Irish town in America is Scituate, Massachusetts, where nearly half of the town's residents are of Irish heritage. The secret, surprisingly, is in seaweed. In 1847, an Irish American fisherman spotted in the nearby waters a type of seaweed he recognized as Irish moss, used in Ireland for making both ice cream and beer. The timing was perfect, for many of the Irish immigrants just then arriving to escape famine were skilled at harvesting and processing the moss. An industry was born, and the town boomed with new arrivals. The trade stayed strong for over a hundred years, helping to build a town that maintains pride in its Irish American roots to this day.