St. Patrick's Day is coming up on March 17. But why do we celebrate the Irish holiday? Here's what to know, plus food deals you can snag in Arizona

The spread of St. Patrick's Day celebrations in the U.S. was a way for Irish immigrant communities, who in the 19th century faced discrimination and opposition, to stake that ground, he says: “It’s a kind of immigrant Irish way of combating nativist antagonism against them.”