This Day in History: br First St. Patrick's Day Parade March 17, 1762 The first St. Patrick's Day parade br is widely regarded as having been br celebrated in New York City by Irish br soldiers serving in the British army. The day honors the br patron saint of Ireland, br who was born to a Christian br family in Britain in the 4th century. St. Patrick is credited br with converting almost all of br Ireland to Christianity before his death. One the most revered br legends about the saint is his br explanation of the Holy Trinity br using a three-leafed Shamrock. Early Irish immigrants br brought his feast day br with them to America. According to the National br Retail Association, Americans br spent nearly $6 billion for br St. Patricks Day in 2018.