To hear Chris Marty of Chicago’s Best Intentions describe it, the provenance of Angostura bitters shots had the inevitability of kindergarteners eating Play-Doh. “It’s in front of you, it’s delicious, it goes in most cocktails and you realize, ‘I like the way this tastes in small amounts, what would it be like as a shot?’” Marty says. And before you know it, you’ve popped off the inner plastic top of the Angostura bottle, and poured yourself an ounce.

What’s slightly less apparent is how Wisconsin became the epicenter for shots of Angostura bitters; the state sells more of those dasher bottles per capita than any other—and it’s not purely because of the Badger State’s enthusiasm for the Old-Fashioned.

Nelsen’s Hall and Bitters Club on Washington Island, located on Wisconsin’s side of Lake Michigan, has been pouring Angostura shots by the ounce since 1920. As with so many odd drinking traditions, the practice began as a means of circumventing Prohibition. The bar’s owner, Tom Nelsen, an immigrant from Denmark, brought Angostura to the island and got away with serving the shots as tonics for stomach issues. The concept wasn’t so farfetched, in that the bitters were originally concocted as a health aid by Johann Siegert in Venezuela in 1830. (Since 1845, they’ve been made in Trinidad.)

Despite Nelsen’s far-flung location, it’s become a favorite destination for vacationers, who easily double the island’s 720-person population every summer. In the high season, Nelsen’s will go through five or six 16-ounce bottles of Angostura in a day, selling shots at $4.50 apiece. Anyone who does a shot gets their name in a 50-year-old ledger and receives a membership card to the Bitters Club.

In the winter, when there are only two daily ferries, there might be fewer patrons, but owner Robin Ditello says her regulars keep coming for the shots. “It’s still a stomach tonic,” she says. “And we’ve cured many hiccups with it in this bar.” Apparently, a shot of bitters and a lemon wedge to the mouth are just the trick.

While plenty of other bitters companies have tried to get in the game at Nelsen’s (Ditello says she’s amassed 20-odd samples of other brands in her office over the years), the restaurant, as tribute to its founder, has only ever served Angostura. And its predilection for shots from those paper-wrapped bottles has spread around the state.

“It’s not on the menu or advertised, but if someone asks for it, we surely give it to them,” says Kat Cary, general manager of Boone & Crockett in Milwaukee. An hour to the west, Thor Messer, bartender at Merchant in Madison, says that the shots are most often called for by bartenders and bar regulars. He’s seen them in cocktail bars like Lucille and Gib’s, as well as in dives, like Argus.

While cocktails like Giuseppe González’s Trinidad Sour and the aptly-named Angostura Sour from Cure in New Orleans lean heavy on Angostura —they both call for an ounce and a half—shooting the bitters on their own hasn’t seen the same popularity outside of Wisconsin. But when Chris and Calvin Marty, brothers who grew up in Wisconsin, opened Best Intentions in 2015, rather than opting for Fernet or even the local bitter, Malört, they put Angostura shots on tap, becoming the first bar in the country to do so.

The Marty brothers negotiated with the local distributor to order Angostura by the five-gallon drum, which they order in 20-gallon drops. The shipments come alone on a truck, marked “flammable” and “dangerous,” evidence that the TTB still doesn’t know how to deal with bitters. “It’s just shy of 90 proof, but it won’t light on fire,” Marty says, with understood knowledge of this fact. “I can only assume it wouldn’t help in a fire.”

The pressure of the English ale-style pump tap gives the Angostura a little bit of aeration and froth, but most people probably won’t notice. “It is way up at the top, intensity-level wise,” says Marty. “A lot of people are taken aback when they drink it and then a lot of other people drink it and say, ‘Ooh, tastes like Christmas!”