The borders between Canada and the US might be closed, but that didn’t stop two breweries located on opposite sides to create a beer honoring the century-long friendship between Nova Scotia and Boston.

The abbey-style ale is a collaboration between Big Spruce Brewing of Baddeck, Nova Scotia, and Boston’s Harpoon Brewery that began last year when the two businesses connected following a Christmas tree lighting ceremony in Boston.

Every year, Nova Scotia gifts a tree to Boston, to show the province’s gratitude for the help Bostonians provided after the Halifax Explosion on Dec. 6, 1917.

Caused by the collision of two wartime ships (one filled with explosives) the blast killed about 2,000 people, wounded another 9,000 and flattened a huge portion of the city. In the hours after the explosion, Boston sent a group of medical experts and supplies to lend aid in Halifax.

“Fermented on a Belgian yeast to note the fact that there was a Belgian ship involved in the explosion,” said Jeremy White of Big Spruce. “It was also brewed with a little bit of spruce tips to kind of give it that quintessential Big Spruce touch, Nova Scotia touch, if you will.”

“People know that there’s this giant Christmas tree and it’s beautiful and maybe that it comes from Canada, but they don’t really know the back story,” said Charles Storey, president of Harpoon Brewery. “As soon as people learn the back story, it provides such a profound connection.” Storey expresses the importance for people to know about the history of how these two port cities came together.

The beer is available across the United States and Canada.