Bourbon is quite possibly the only drink that is truly and uniquely American. While beer and wine, gin and vodka, and even other types of whiskey can be made in America, bourbon must be made in America; it’s the law. But that law wasn’t passed until 1965. From the first distillers in 18th century Kentucky to the industrialized operations of today, bourbon’s journey has been long and steady, and despite frequent challenges from wartime rationing to peacetime tax hikes, from teetotal preachers to crooks, criminals, and carpetbaggers, from political shakedowns to corporate raiding, bourbon has managed to thrive. Bourbon isn’t just an American drink; it is America’s drink. On the frontier it was ubiquitous – it was used as medicine and even as currency. From alleviating some of the harshness of the winter at Valley Forge to being stilled and traded by both Reb and Yank, whiskey fortified our soldiers at war. Bourbon and the United States grew up together; they are almost exactly the same age and their stories are intertwined. If bourbon and the United States had somehow grown up independently, the former would still be a drink and the latter would still be a country, but they would not be the drink or the country that they are. Without bourbon, America would be markedly different. But what is Bourbon?
Bourbon is whiskey, made in America, from at least 51 percent corn and aged in new, charred oak barrels. All bourbon whiskeys are made of more than 51 percent corn but not more than 90 percent. Corn is always the primary ingredient and is the source of the sweetness that makes bourbon unique and distinctive among other types of whiskey. Many 
whiskey labels make reference to choosing only the finest grains. But let’s be realistic: distillers do not buy corn as a grocery, they buy it as a commodity. According to Charles K. Cowdery in “Bourbon Straight: The Uncut and Unfiltered Story of American Whiskey,” all Kentucky distillers use the same corn: USDA Grade 2. There are five grades in all, so Grade 2 is near the top and certainly better than cattle feed, but probably not as good as what people choose to eat. That corn is then combined with rye, wheat, or barley in what is called the “mash bill.” The term “mash bill” roughly means “recipe” and is an important distinction for American whiskey. In other countries, individual grains are milled and mashed separately and combined after distillation. It is only in this country that the ingredients are combined in the mash before fermentation and distillation. Another practice unique to American distillers is in outsourcing the malts. While Scotch distillers do their own malting, American distillers choose not to and buy their malts from companies, often outside of Kentucky, known as maltsters.
When we talk about a mash bill or just mash, drinkers familiar with American whiskey will make a connection to the phrases “sour mash” or “sweet mash” that adorn whiskey labels. Sour mash is unique to America and refers to a process, as opposed to an ingredient. The invention of the sour mash process is credited to a Scottish chemist, Dr. James Crow (founder of Old Crow), though some have attributed the development of sour mash to Jim Beam or even Jack Daniel’s, as Gavin D. Smith does in “The A-Z of Whisky.” However, the general consensus points to James Crow, who immigrated to the United States in 1823 and almost immediately began making whiskey. What he discovered was that by taking the “setback” or “slop” (so called because it was frequently fed to pigs), which is a by-product of distillation, and adding it to a new mash he could reliably control the Ph levels of the whiskey. With the sour mash process, James Crow achieved an unprecedented level of consistency and quality control. The combination of setback to a new mash creates a sour odor, hence the name “sour mash.” According to Cowdery, modern technology has made this process obsolete, but whiskey is a traditional industry so many distillers still use it. The sweet mash process on the other hand, is simply not adding setback to the mash. There are very few sweet mash bourbons made today, but the sour mash process is universal.
When the mash has been distilled and the distiller is sure that he has the spirit that he wants, there is still a lot more to do. New, unaged whiskey is clear and is not as flavorful as a whiskey that has been aged in a barrel of wood. By law, bourbon must be aged for at least two years in new, charred oak barrels. New barrels impart more flavor than used barrels do, which is why one rarely sees a bourbon as old as many Scotch whiskies. Bourbon does not need as much age as Scotch and, at a certain point, will reach a peak beyond which the drink begins to taste worse. The charring of the barrels also serves some important functions for the whiskey. As the liquid in the barrels heats and cools with the ambient air, it expands into the wood of the barrel and contracts back out of the wood again. Two important things happen to the whiskey as it interacts with the wood. First, the char filters out many elements called “congeners,” which include fusel oils and aldehydes that can have deleterious effects on both the drink and the drinker. Secondly, the char imbues the whiskey with even more flavor through what distillers call the “red layer.” In “American Still Life: The Jim Beam Story and the Making of the World’s #1 Bourbon,” Paul F. Pacult explains that naturally occurring sugars in the wood become caramelized during the charring, or “toasting” of the barrels. These caramelized sugars give the beverage more sweetness and a distinct vanilla flavor.
In the early 19th century, most whiskey would have been unaged when it reached the consumer. The most popular and plausible explanation of how distillers discovered the benefits of barrel aging is that whiskey often tasted better in New Orleans than it did in Cincinnati. Whiskey shipped to New Orleans would not only have spent more time in the barrel than whiskey served closer to home, but it would have sloshed around the inside of the barrel almost continuously in even the smoothest forms of frontier transportation. No one knows who first discovered this phenomenon, but we do know who first embraced it. Dr. James Crow, the same man who developed the sour mash process, became the first distiller to always and only barrel age his whiskey. Another innovation attributed to James Crow that is essential to good whiskey is cleanliness. A clean and sanitary still contains much less bacteria that can negatively affect the flavor and reduce the quality of the beverage. According to Charles Cowdery, reduction of bacteria and other unwanted cultures and microorganisms also provides consistency from one batch to the next. Quality and consistency are why a hygienic operation is so fundamentally important. It has nothing to do with safety, as harmful bacteria cannot survive in a finished product as alcoholic as whiskey. This is undoubtedly an important aspect of distillation, but analysis shows that it cannot be accurately attributed to Dr. Crow. First of all, distillers of Scotch, gin, rum, cognac, etc. most assuredly would have made the same discovery. But even American whiskey distillers were familiar with the importance of 
sanitation long before James Crow. In “The Practical Distiller or an Introduction to Making Whiskey, Gin, Brandy, Spirits, etc.,” author and distiller Samuel McHarry wrote “Cleanliness in every matter and thing, in and about a distillery becomes an indispensable requisite, without a strict observance of which the undertaker will find the establishment unproductive and injurious to his interest.” That book was published in 1809, more than ten years before Dr. Crow arrived in the United States. However, Dr. Crow might have been the first to apply the principal of cleanliness on a large scale. McHarry noted that in the 20 years (at the time of writing) that whiskey had been available in large quantities in the seaport towns, it had not been good whiskey. Bad as it may have been though, it was widely available to the point that whiskey was in 1809, “…the second great article of commerce in the states of Pennsylvania and Maryland.” With so much whiskey being made in those states, one wonders how the less populous Kentucky became the whiskey capital.
Why Kentucky? There was no cultural distinction. Kentucky was settled largely by the same German immigrants who populated the Mid-Atlantic states and the same Scots-Irish immigrants who populated the South. A popular explanation is that distillers in Pennsylvania moved to Kentucky as a result of the Whiskey Rebellion of the 1790s. Historically, this is a weak and unlikely explanation for a few reasons. First of all, distillers like Evan Williams and Elijah Craig were already in Kentucky before the Rebellion. Second, if one were to move somewhere to make whiskey free from the nuisance of federal laws and taxation, it would not make sense to move someplace subject to the same laws and taxation. Third, as noted above, Pennsylvania had a robust distilling industry in 1809, after the Rebellion was over and the tax that caused it had been repealed. The correct explanation probably has a lot more to do with water.
A proud Kentuckian will proclaim that it is their limestone water that makes their whiskey so good. He will probably also say something about fast horses and blue grass (the actual grass, not the music). At first all of this sounds like wives’ tales and folklore, but there is actually some science to it. Limestone water is ground water that has been naturally filtered by the limestone aquifers that it comes from. This water is good for whiskey production because it contains a high level of calcium carbonate. According to Pacult, calcium carbonate works particularly well with yeast cells during the fermenting. Apparently, it is also this calcium-rich water that makes the grass blue and the horses strong. But it is not only ground water that is important; running water is perhaps even more important. Kentucky has more than its share of streams and navigable waterways, and both have been essential in establishing bourbon as America’s drink. Sam K. Cecil states in “Bourbon: The Evolution of Kentucky Whiskey” that early distilleries began as gristmills. Before modern mechanization, mills were powered by natural streams diverted to turn a water wheel. In the frontier days, many farmers lacked cash to pay the mill so they paid in a portion of the grain that had been milled. The mill operator then turned to distillation as a way to use all of that excess grain. In Kentucky, those mills/distilleries usually had ready access to navigable waterways. In other states, a distiller was limited to selling only what could fit on a pack horse or, in the best case, a wagon. But Kentucky distillers were often only limited by what could fit on a flatboat, which were sometimes more than 70 feet long. While whiskey in North Carolina might struggle to get through the hills to the next town, great quantities of bourbon could simply float downstream all the way to New Orleans – a city which helped secure bourbon’s identity.
It is a common misconception that bourbon must come from Bourbon County, Kentucky. Legally, bourbon can be made anywhere in the United States. The name bourbon however, is associated with the county, but not the modern one. The Bourbon County today does not actually have any distilleries. In the 1790s, Bourbon County referred to an area that now is comprised of over 30 modern counties. It was the whiskey that came from this part of Kentucky that became known as bourbon, or whiskey from “Old Bourbon” to reference the fact that the county had been broken up and split into many counties. But why was it whiskey from that specific part of Kentucky that became so well known that its name eclipsed all other whiskeys in this country? As stated earlier, Old Bourbon distillers, via navigable rivers, had ready access to large markets, particularly down the Mississippi River. And again, as stated earlier, the trip down the river gave the whiskey a beneficial experience in the barrel and a flavor that most other whiskeys at the time didn’t have. The French residents in New Orleans and other smaller towns in what, before 1803, was still French territory developed a taste and created a large market for whiskey from Old Bourbon. Charles K. Cowdery suggests that the French liked bourbon because, lacking other alternatives, bourbon’s sweetness provided a suitable substitute for cognac. From an historical perspective, this is a sound theory. Between the French Revolution in 1789 and the ultimate defeat of Napoleon in 1815, France and Britain were in a nearly constant state of war, and the Royal Navy was good at its job. It is difficult to imagine that much cognac made its way across the Atlantic in those days. Whatever the reason, the French in Louisiana bought a lot of whiskey and they called it by the one word on the barrel that they definitely knew: bourbon, the name of their once great – but by the 1790s exiled or dead – royal family. The name bourbon became initially attached to the drink because of the place of its origin, but it stuck because of the association so many people in Dixieland made between good whiskey and the word “bourbon.”