Visit any bar or party on St. Patrick’s Day and you’ll no doubt be offered a celebratory pint of green “Irish” beer. In order to prepare for this upcoming Patty’s Day, here are 5 fun facts about the American tradition that is green beer.

It’s actually an American tradition.

Although the drink itself is to celebrate the Irish holiday of St. Patrick’s Day, the concept of doing so by drinking green beer is an American tradition, originally started in Washington.

The best way to get green beer is actually with blue food coloring.

While it’s pretty common knowledge that yellow and blue make green, most people assume that green food coloring is used in most of the beer. However, since lighter beers tend to have a yellow hue, adding blue coloring creates a the bright green color more commonly seen.

It was created by a doctor.

While the first mention of green beer was in a Spokane, Washington, newspaper in 1910, the drink is more commonly credited to Dr. Thomas Curtin, who served green beer at a New York party in 1914. However, instead of using blue food coloring, Curtin mixed the beer with diluted, blue detergent. Despite that alarming fact, the green drink was a hit and a tradition was born.

The Irish have their own drinking tradition: “Drowning the Shamrock.”

The shamrock, or four-leaf clover, is one of the most recognizable Irish symbols and often referred to as a token of good luck. Because of this, the Irish believe that by floating a shamrock in your whiskey before drinking it on St. Paddy’s Day guarantees a year of good luck.

The tradition of St Patrick’s Day was originally a feast, not drinking.

The feast has always been held on March 17 as a way to honor Saint Patrick on the anniversary of his death. Because this date coincides with Lent, feast goers were allowed to temporarily put their food and alcohol restrictions on hold in order to celebrate. This eventually evolved the feast into the drinking holiday we know today.