Just off the coast of Winsconsin, in the frigid depths of Lake Michigan, sits Washington Island, a tiny island home to just over 700 people. Despite the small, three-digit population, Washington Island outsells every other town in the world when it comes to the amount of Angostura bitters consumed per capita. What could possibly be driving such impressive sales in such a small, remote place? Turns out the answer points back to one bar — Nelsen’s Hall — and it’s not because they’re dishing out thousands of Old Fashioneds.

Rather than garnering the title of largest Angostura purveyor by using the ingredient in an abundance of cocktails, Nelsen’s is famous for kick-starting the bizarre tradition of taking shots of Angostura. Not shots containing various spirits and a dash or two of Angostura, but 1.5-ounce servings of straight-up bitters.

First opened as a dance hall in 1899, Nelsen’s Hall was founded by Tom Nelsen, who expanded the space into a bar three years later. Less than two decades later, when Prohibition threatened the security of his bar, Nelsen was forced to get crafty in coming up with ways to remain open. Instead of operating with an alcohol license — which had for obvious reasons been stripped away — Nelsen acquired a pharmaceutical license as a sneaky way to legally sell the shots.

Get the latest in beer, wine, and cocktail culture sent straight to your inbox.

As Angostura bitters are only intended to be used a few drops at a time, at the time of Prohibition, they were classified as a “stomach tonic for medicinal purposes,” despite the fact that they contain 44.7 percent alcohol by volume. As such, Nelsen acquired a pharmaceutical license that allowed him to legally distribute Angostura as a medical tincture.

“Medicinal tinctures are usually taken in smaller doses,” Sarah Jaworski, whose parents have owned the bar since 1999, explains in an interview with Atlas Obscura. “But since Angostura bitters are 90 proof, he was able to legally sell it as a tincture. He just sold it as shots.”

Despite the legal, albeit murky, loophole, Nelsen’s operations were not able to fly completely under the radar; the police were known to regularly come sniffing around, though they were unable to ever shut down the bar. On one occasion, Nelsen was even made to appear in court to prove the legitimacy of his license. Allegedly, he defended himself by explaining the bitters’ healing properties before pouring a shot for the judge, who (properly) responded with disgust upon taking it, asking “Who would ever want to drink this?”

Even once the 18th Amendment was repealed and the bar was able to resume its service of proper shots, the Angostura shot lived on at Nelsen’s. Up until his passing, Nelsen was said to consume a full pint’s worth of Angostura shots every day.

Today, the Angostura shot remains one of the most popular menu items at Nelsen’s Hall, which is known to go through three cases of bitters on busier weekends. Annually, the bar sells upwards of 10,000 Angostura shots; every person who chooses to partake earns a spot in the “Bitters Club” and receives a card certifying that they have “taken ‘the Cure’ by consuming the prescribed measure of bitters and as such [are] a fully initiated member of the Bitters Club.” Upon signing their own name in a decades-old book, shot-takers are “considered a full-fledged Islander and entitled to mingle, dance, etc. with all the other islanders.”