Well, by law anyway:
For around 150 years, the words Tennessee Whiskey have meant one thing: You take bourbon fresh from the still and then filter it through sugar-maple charcoal before you seal it up in a new, charred, white oak barrel to age.
It’s quite simple, and for decades that was the accepted definition through handshakes and likely the clinking of glasses over sawdust floors. It was essentially a marketing ploy to distinguish our product as something distinctly different from that other juice being made up north in Kentucky.
Among the distillers who held to this gentleman’s agreement were Jack Daniel, who claims to have first embraced this particular use of charcoal filtering that’s called the Lincoln County process, along with George Dickel and Charles Nelson.
There might or might not have been other distillers who adhered to this understanding, but the significance of these three is that they continue to subscribe to that narrow definition today.