Tennessee whiskey and the Lincoln County Process
If you have ever wondered how Jack Daniels differs from a bourbon, the answer fits into one production step called the Lincoln County Process. It is this step that defines the entire Tennessee whiskey category and means that, although the style technically meets every requirement of bourbon, it stubbornly goes by a different name. The story is more interesting than it seems, and the difference in flavour, though subtle, is real.
Tennessee whiskey is essentially a bourbon
Let us start with a fact that surprises many people: every Tennessee whiskey meets the legal definition of bourbon. Both styles share the same rules. The mash must contain at least fifty-one percent corn. Distillation cannot exceed eighty percent alcohol. The spirit goes into new, charred American oak barrels, with a maximum strength of 62.5 percent when filled. Bottling is at a minimum of forty percent. These are exactly the same requirements that define bourbon. I cover bourbon itself in detail in bourbon explained.
So if Tennessee whiskey meets the definition of bourbon, why is it not called bourbon? Because there is one extra stage that bourbon does not require, and which Tennessee producers consider the heart of their identity. That stage is the Lincoln County Process.
What the Lincoln County Process is
The Lincoln County Process is the filtration of fresh spirit through a thick bed of sugar maple charcoal before the spirit goes into the barrel. We are talking about spirit straight from the still, still clear and unaged, known as new make. Instead of pouring it straight into the barrel, it is run slowly, drop by drop, through a column packed with maple charcoal, sometimes several metres tall. In the case of Jack Daniels this percolation can take many days.
The mechanism is purely physical. Sugar maple charcoal has a highly porous structure and a huge surface area that binds some of the compounds responsible for the harsh, raw edges of young spirit: higher alcohols known as fusels, aldehydes and certain esters. The result is a smoother, gentler, rounder spirit, before it has even begun to mature in wood. Hence the second name for the process: charcoal mellowing.
Importantly, this is not the same as the chill filtration applied to finished, mature whisky just before bottling. The Lincoln County Process happens right at the start, before the barrel, and shapes the raw material rather than the final product. I cover chill filtration and colouring in chill filtration and colouring.
Does it really change the flavour
Yes, though the change is subtle and a matter of debate. Supporters say charcoal mellowing removes harshness and sharp notes, giving a softer spirit with a light, faintly sweet note that some people associate with maple smoke or burnt sugar. Sceptics argue that after years of barrel ageing the difference is hard to catch, because it is the wood that accounts for most of the flavour of any American whiskey.
The truth probably lies in between. Charcoal filtration genuinely changes the profile of the new make, reducing raw, volatile compounds. But it is still the barrel, time and the Tennessee climate that do the most for the final character. If you want to sense the effect of mellowing, look in Tennessee whiskey for exactly that smoothness and roundness compared with the spicier, more rugged bourbon from neighbouring Kentucky. I cover where whisky flavours come from in the first place in where whisky flavours come from.
The law that codified a tradition
For most of its history the Lincoln County Process was a custom, not a requirement. That changed in 2013, when the state of Tennessee passed a law regulating what may be called Tennessee whiskey. From then on, to bear that name a spirit must, among other things, be filtered through sugar maple charcoal before ageing, have a mash of at least fifty-one percent corn, mature in new charred oak barrels within the state of Tennessee and be distilled to no more than eighty percent alcohol.
A legal curiosity: at the federal level, the United States has no separate, official definition of Tennessee whiskey in the standards of identity for distilled spirits. The category exists primarily thanks to state law and trade agreements that recognise it as a distinct type of American whiskey. It is a rare case where the name is decided more by state regulation and tradition than by federal definition.
One exception to the rule
Like every good rule, this one has an exception. All Tennessee whiskey producers must use the Lincoln County Process if they want to use the name, with one exception: the Prichards distillery. Amusingly, it is located in Lincoln County itself, after which the process is named. Prichards obtained an exemption because its owner argued that his ancestor, from whom the recipe descends, never used charcoal filtration. Tradition versus tradition, and the law sided with the older one.
Where the name Lincoln County comes from
The name comes from Lincoln County in Tennessee, where the technique was already in use in the nineteenth century. Interestingly, the Jack Daniels distillery itself, the most famous producer of the style, ended up outside Lincoln County as a result of later changes to administrative boundaries, in Moore County. The name of the process stayed with the original place where it was born.
The big two and the rest of the field
The best-known Tennessee whiskeys are Jack Daniels and George Dickel. Both use charcoal mellowing, but in slightly different ways. Jack runs fresh spirit through charcoal at ambient temperature. Dickel goes a step further and chills the spirit before filtration, believing that a lower temperature gives a smoother result. It is a small nuance, but for someone calibrating their palate it can be a fascinating point of comparison.
In recent years the category has been growing, as more and more small Tennessee distilleries take up the style, treating the Lincoln County Process as a local mark of quality and identity. That is good news for tasters, because it gives more opportunities to compare different interpretations of the same idea.
How to taste it
The best way to understand Tennessee whiskey is to set a glass of Tennessee whiskey beside a classic Kentucky bourbon of similar age and strength. Focus on the texture and on how the spirit arrives: Tennessee whiskey often feels smoother, rounder and softer on entry, while bourbon tends to be spicier and more rugged. In GustoNote you note the strength, sweetness, woody notes and your impressions of each glass, and after a few comparisons you will see whether you really sense the effect of charcoal mellowing. It turns an abstract argument about process into a concrete, personal tasting experience. You will find a full overview of the world’s whisky styles in whisky of the world.