American whiskey production grew out of the settlement of the Ohio River Valley. After independence, white settlers began to move west of the Appalachian Mountains, which had previously been restricted by the British government, eager to keep their colonists close to the coast where they could be more easily taxed. The farmers who grew crops in the extremely fertile region, including lots of corn, rye, and barley, found that it wasn't economically feasible to transport their grain east of the mountains where most of the demand for their products was to be found. However, if those grains were fermented and distilled, the resulting whiskey had a lot more value per pound, meaning that money could be made even after shipping it over the Appalachians. This fueled the almost insatiable appetite for liquor during the 19th century, when the average American drank about five gallons of absolute alcohol in a year (this translates to roughly one 750 mL bottle of 80-proof liquor in a week).
|Column still at Wild Turkey via Alcademics|
Now there are very tight regulations about how bourbon and rye whiskeys must be produced if the distillers want to label them as 'straight' bourbon or rye whiskey. First, bourbon must be made from a mash of between 51 and 80% corn, with the balance being made up with rye or wheat (the flavoring grain) and malted barley (the enzymes in malt convert starches from the other grains into fermentable sugars). Distillation must be to no more than 160-proof (80% alcohol) and the distillate must be diluted to no more than 125-proof (62.5% alcohol) for aging in new charred oak barrels. At that point it can be called bourbon whiskey. To gain the 'straight' moniker, the bourbon must be aged for at least two years. Bottling, whether straight bourbon or not, must be at least 80-proof (40% alcohol). American rye whiskey conforms to the same requirements, except that the mash must contain at least 51% rye, with the balance being made up with corn and malted barley.
Maker's Mark, but I generally prefer Weller bourbons. At the beginning of the rye recipe bourbon spectrum, go for something like Buffalo Trace with 8% rye in its mash bill. Rye flavors will be present, but tend to give way to corn sweetness. In the mid range, Wild Turkey, Ezra Brooks, and Evan Williams bourbons are all made from a 13% rye mash bill and most of Jim Beam's whiskeys are made with a 15% rye mash bill. Here rye becomes a more significant presence, but is still in balance with the corn. Above this, we enter what is generally thought of as 'high rye' territory. Four Roses uses two different 'high rye' mash bills, one at 20% and another at a whopping 35% (the latter is the source for Bulleit bourbon). Jim Beam maintains a legacy 30% rye mash bill for their Old Grand Dad and Basil Hayden expressions. In those whiskeys, rye will be more more prominent, making the bourbon both more spicy and less sweet.
From there exists a bit of a gap until you hit rye whiskeys. At 51% rye in the mash bill, Jim Beam (and their Old Overholt label) Rye and Sazerac 6 Year are just over the legal line. So while these are definitely rye whiskeys, with all the spicy herbal flavors that implies, they also retains a fair amount of corn sweetness, making them a good bridge between the two styles of whiskey. From there, it's a jump to whiskeys made with 65% rye in their mash bills - Rittenhouse, Wild Turkey, and Russell's Reserve. These are very spicy and much drier than bourbon. Finally, LDI/MGP uses a 95% rye mash bill for whiskey that is now released by a wide range of independent bottlers from Bulleit to Willett to Templeton to Redemption to George Dickel (if it's a new rye whiskey brand, then it's probably from LDI/MGP - they're the only distiller with spare rye capacity). To get above that, you'll have to turn to Canada - Alberta Distillers makes a 100% rye mash bill whisky. While usually blended into Canadian whiskies, it is also sold as Alberta Premium and now bottled by a number of American independent bottlers, ranging from Jefferson's to Masterson's and Whistle Pig.
The other axis to look at is age. Because bourbon and rye are aged in new charred oak barrels, they soak up flavor very quickly. This means that even a year or two can make a significant difference in flavors. It's best to keep the mash bill of the whiskeys you're comparing the same or similar to remove that variable from the equation. Many distillers offer whiskeys from the same mash bill at different ages, such as Buffalo Trace (~4-5 years old) and Eagle Rare (10 years old) or Wild Turkey (6-8 years old) and Russell's Reserve (10 years old) or Weller Special Reserve (~7 years old) and Weller 12 Year. Older whiskeys will tend to be more oaky and tannic, but also with more caramel and toffee flavors.
While this feels like a lot of information, hopefully it gives you a few places to start or expand your exploration of American whiskeys. Bourbon and rye are fantastic choices these days because there are still so many great whiskeys available for under $30, making it a very economical way to drink well.