There was a time when the quality of whiskey was judged by how long it took to get your breath back after a good swallow. Fortunately that time is behind us and these days the American whiskey industry is booming.

The Kentuckians and Tennesseans I’ve met who make American whiskey are a friendly lot, often funny, and always ready to talk about making whiskey. A favorite answer to the question, “How many people work here?” is “About half.” Many carry the hills and hollows they come from in their speech, flattening the As and rounding the Is. A few come to work in suits, but most wear khakis or jeans and thick-soled shoes or steel-toed boots, depending on whether they spend more time in the stillhouse or the rickhouse. There’s lots of climbing in distilleries – grain silos and column stills reach as high as five stories and 30,000-gallon fermentation vats have their bottoms on one floor and their tops on the next. Barrels weigh more than 500 pounds when they’re full and steel toes offer some protection but skilled handling is the surest.

At its core, distillation is the same now as in the fourth century B.C. when Aristotle wrote about using the process to render seawater drinkable; but to create the complex character that marks fine whiskey, the variables are considerable and maturation is critical. The basic principle of distillation is this: heat a fermented liquid and the alcohol boils at a lower temperature than the water. The boiling alcohol separates and rises as vapor which, when cooled, returns to a liquid state.

Distill the fermented juice of fruit and you have grappa, applejack, armagnac, brandy and cognac. Distill molasses and you have rum. Distilling fermented starchy grain up to 160º yields whiskey, also known as brown goods within the trade. Distilling grain at 190º strips out flavor-bearing impurities, collectively called congeners, and yields gin and vodka, or white goods. Flavor is restored to gin with the addition of juniper berries and other botanicals. Vodka remains without taste or aroma unless flavorings are added and you can buy most any flavor you want, from sweet tea to marshmallow.

A distinguishing factor about whiskey is that by law nothing can be added to impart either flavor or color. Both result, instead, from the manipulation of all those variables. Flavor is first defined in the fermentation vat by mash bills and yeast and then blooms in the barrel.

Whiskey is distilled at a lower temperature to retain what’s known to the trade as congeners and what’s known to us as toxins. These are the components that make whiskey whiskey and their presence is surprisingly minuscule, measured in ratios of one part per million. They render new whiskey undrinkable until aging in charred American oak barrels transforms the toxins and releases the flavor. The deep amber color is extracted from the barrels and as more years go by, deeper tones mark the amber. Some say as much as 80 per cent of whiskey’s flavor comes from what happens to it during aging as the congeners react with the elements—charred wood, sunshine, mists rising off rivers, hot summers, cold winters, breezes drifting through open windows, rain, the waning of the moon.

American distilling started out as family businesses and a tracery of those bloodlines marks current brand names and distilleries: Jim Beam, George Garvin Brown, Pappy Van Winkle, George Stagg, Colonel Blanton, W.L. Weller, Elmer T. Lee, Jack Daniel, George Dickel, James Crow, Booker Noe, and Jimmy Russell, to name but a few. Some made fortunes and others just make good whiskey but all have worked together to forge an industry that has moved beyond its own flaws to steadily improve the spirit identified as American whiskey.

A bottle of American whiskey gets its start on an early spring morning with the sowing of a new crop of corn and a prayer lifted to Mother Nature. When the fermented grain has been distilled and depleted of alcohol, the spent mash is still rich in nutrients and is dried, bagged, and returned to the farm as livestock feed. As the process cycles through, a bottle of whiskey is tended by many hands—coopers, grain handlers, mash hands, yeast propagators, still hands, supervisors, bottlers, master distillers, warehouse hands, marketers, executives, brand managers, and yes, accountants, for more than half the cost you pay for every bottle is claimed by taxes.

Most American whiskey distilleries are located in Kentucky and Tennessee but not all. Garrison Brothers is distilling award-winning cowboy bourbon in Hye, Texas and that’s only one of more than 200 artisan or craft distilleries located across the country, many making whiskey and some making good whiskey. If you want a distillery tour, then Kentucky’s Bourbon Trail is a good place to start. There are currently eight distilleries on the Trail that have visitor centers and offer tours.

The heart of Kentucky is horse country as well as bourbon country and the thoroughbred character of both is sometimes attributed to the local water that filters through a ledge of limestone running both above and underground through Kentucky and into Tennessee. The limestone extracts deleterious elements like iron, which can turn whiskey black as night and imparts calcium and other minerals that nourish the enzymes critical for good fermentation of the mash bill.

In central Kentucky where a dozen distilleries contribute to the world’s supply of bourbon, hills of bluegrass roll up and down before giving way to sweeping meadows and shady groves of oak, poplar, maple and cedar. Two-lane roads connecting towns of a few thousand or a few hundred are as curvy as the coils of a moonshiner’s copper worm. Distillery warehouses ride the hilltops and nestle into hollows, their stark symmetry contrasting with the intricacies of the landscape. They’re made from metal or brick and most have windows banded around each of the seven or fewer stories to be opened or closed depending on what’s deemed best for the whiskey maturing inside.

Farther south in the highland ridge foothills of the Cumberland Plateau toward Lynchburg, where Tennessee whiskey is made, the landscape is equally captivating and home to Tennessee walking horses, famous for their high-stepping gait. There are only two Tennessee distilleries, Jack Daniel and George Dickel, separated by a dozen or so miles and twice as many Baptist churches.

While the whiskey they make may look like bourbon and taste like bourbon, technically it’s not. It was labeled bourbon until 1941, but the Tennessee legislature thought they’d get a leg up on their bourbon competition and call their whiskey Tennessee whiskey. Federal regulations require that both bourbon and Tennessee whiskey be distilled from a mash bill containing a minimum of 51 per cent corn (in practice most contain closer to 70 per cent), be distilled out at no higher than 160 proof, contain no additives other than pure water, and be aged in charred oak barrels for a minimum of two years. Tennessee whiskey, unlike bourbon, is also dripped through ten feet of fresh maple charcoal before it’s barreled, taking almost as many days on the slow trip down. This is called the Lincoln County Process and is what distinguishes Tennessee whiskey from bourbon. That and Tennessee law.

To make the charcoal, split maple wood is stacked and ignited with white dog, which is what new distillate is called when it first comes off the still in a raw and flammable state. The wood is allowed to burn through before being hosed down and left to smolder until cool enough for mincing. The leaching vats are filled with fresh charcoal every six months and as the white dog passes through it, a hint of smokiness is imparted and some of the harshness of the congeners is diminished even before barrel aging. Jack Daniel’s Gentleman Jack brand is leached a second time after aging and before bottling.

Jack Daniel stood only five feet two and wore a size four shoe but in the time since his demise his presence has grown bigger than life. In 1895, he chose a square bottle for Jack Daniel’s No. 7 to represent a square deal. Both deal and bottle are still square. Some say the number seven was chosen for the life-long bachelor’s seven girlfriends. One thing is for sure: If you ask people around the world to name a bourbon, most will name Jack Daniel’s, unaware of Tennessee’s own special regulations. If it looks like bourbon, and tastes like bourbon….

American whiskey is so continuously woven into the fabric of American culture that tracing its development draws a profile of America itself – feet planted in the past and head turned expectantly toward the future. Distillers look to the future for innovation and to conjure what their customers might want by then but their profits rest in the past, in the whiskey that’s already been made and reposes in the warehouse, transforming itself. The industry itself has consistently confounded reports of its own demise; outlasting rings, trusts, false labeling, temperance, Prohibition, and a fickle public.

Whiskey claims a mind of its own and holds its course. Distillers would love a faster turnaround on their investment and search for ways to accelerate aging, hoping for an eight-year taste from four years in the barrel. Whiskey ignores these efforts and continues to choose time as its most favored companion, leaving humans behind to clean the vats, fill out the paperwork, and pick up the tax tab.

Bourbon’s American heritage was officially recognized and recorded in the Congressional Record on May 4, 1964, when United States Representative John C. Watts from Kentucky’s Bourbon County asked his colleagues to pass Senate Concurrent Resolution 19 resolving: That it is the sense of Congress that the recognition of Bourbon whiskey as a distinctive product of the United States be brought to the attention of the appropriate agencies of the United States Government toward the end that such agencies will take appropriate action to prohibit the importation into the United States of whisky designated as “Bourbon whiskey.”

Congressman Byrnes of Wisconsin responded that “what we are doing here is according to an industry in this country the same privileges, if they are privileges, that we have accorded to producers in other lands with respect to distinctive products…I believe this is a proper bill and that we should accord an industry in this country the same rights that we accord similar industries in other countries. It is merely doing for our own, in a sense, what we are willing to do for others.”

He was referring to legislation in Scotland, Ireland, and France that protects local industry by prohibiting the importation of any beverages labeled Scotch, Irish whiskey, or cognac. Likewise, Senate Concurrent Resolution 19 prohibits the importation of foreign whiskies into this country that are labeled bourbon. Bourbon sold in American must be made in America but it’s a common misunderstanding that it must be made in Kentucky. In fact, any state in the union is free to produce bourbon and craft distilleries are making sure of it. Tennessee whiskey, on the other hand, legally can be made only in Tennessee.

On that day in May as bourbon was officially claimed by America and we took our place among the classic distilling countries, the Congressional Record records that Congressman Lindsay of New York thanked the gentleman from Kentucky and offered a poem:

The nectar of Scotch is very urban,
And that of Irish, the cream of Dublin,
But is there a man with soul so dead
Who never to himself has said:
This is my own, my native Bourbon.