What started out as a medicinal tonic is now one of the most popular drinks in the world — and Elijah Craig will be honoring the signature cocktail during its Old Fashioned Week, which starts today.

The bourbon company will donate $5 to the Southern Smoke Foundation, which supports people working in the food and beverage industry, for every post on social media of the drink posted with the hashtag #OldFashionedWeek + you can win a home bar kit as part of the action.

This Campfire Old Fashioned from River House has got us feeling all the fall feels. | @loufoodreviews

What's in it
While its classiness may seem to denote complexity, an Old Fashioned is simply four ingredients: whiskey, sugar, water, and bitters.

A little history
As Derby City's signature cocktail, naturally the 502 lays claim to the birth of the Old Fashioned + its creation is attributed Col. James E. Pepper of the Pendennis Club. It'ss said he invented the drink here before taking it to the Waldorf Astoria in the 1880s.

The recipe is also related to Jerry Thomas, America's father of mixology and author of the first surviving 1830s bartenders guide, "How to Mix Drinks." In the guide, Jerry listed an Old Fashioned "Holland Gin Cocktail" whose ingredients are basically the same as a modern Old Fashioned, except instead of whiskey, he used gin.

In the 1880s, the Chicago Tribune called it "the old-fashioned cocktail" because many requested a whiskey cocktail made "the old-fashioned way." And a star was born.

Now that you know the history, raise a glass at one of these local bars.

🥃 Trouble Bar, 1149 S. Shelby St. | Hit this kick-off party on Mon., Oct. 17 with a build-your-own menu + the "Conor's Usual" Old Fashioned with demerara syrup and bitters.

🥃 Gertie's Whiskey Bar - NuLu, 821 E. Market St. | This take on the Old Fashioned features bourbon that's been infused with brown-butter + finished with a dash of pecan syrup.