St. Patrick's Day is celebrated on March 17, his religious feast day and the anniversary of his death in the fifth century. The Irish have observed this day as a religious holiday for over a thousand years. On St. Patrick's Day, which falls during the Christian season of Lent, Irish families would traditionally attend church in the morning and celebrate in the afternoon. Lenten prohibitions against the consumption of meat were waved and people would dance, drink and feast - on the traditional meal of Irish bacon and cabbage.
The first St. Patrick's Day parade took place, not in Ireland, but in the United States. Irish soldiers serving in the English military marched through New York City on March 17, 1762. Along with their music, the parade helped the soldiers reconnect with their Irish roots, as well as fellow Irishmen serving in the English army.
Over the next 35 years, Iris patriotism among American immigrants flourished, prompting the rise of so-called "Irish Aid" societies like the Friendly Sons of Saint Patrick and the Hibernian Society. Each group would hold annual parades featuring bagpipes (which first became popular in the Scottish and British armies) and drums.
In 1848, several New York Irish Aid societies decided to unite their parades to form one New York City St. Patrick's Day Parade. Today, that parade is the world's oldest civilian parade and the largest in the United States, with over 150,000 participants.
Each year, nearly three million people line the 1.5 mile parade route to watch the procession, which takes more than five hours. Boston, Chicago, Philadelphia and Savannah also celebrate the day with parades involving between 10,000 and 20,000 participants.