Justin, we've used corn as our liquor base here in the colonies because it was the grain of choice.
Contrast that to grain bill in the U.K., where it's rye and barley.
Barley is neat because the 2-row and later/better 6-row varieties have an excess of diastatic enzymes to convert starches to fermentable sugars, which is very important.
To have corn do that, it needs to be malted, where the corn kernels are kept moist long enough to sprout and start their own internal enzyme action, then the sprouts are milled out leaving the corn kernels ready to ferment.
Nowadays, the grain bills of many American whiskies and bourbons have a mix of barley and corn, using the barley's abundance of enzymes to both add flavor and boost the corn's starch breakdown during fermentation.
Bourbon is supposed to have at least 50% corn in the grain bill, but most are considerably higher than that.
There's a long tradition that fuels this. My understanding is that a lot, if not most, of our founding fathers converted a percentage of their given corn harvest into distilled spirits as a matter of practice.
The finished product was used as a means of exchange, and quite popular at that. British taxation of tea was a fore-runner to the 1791 Whiskey Rebellion.
Having said that, I just tried a Japanese whiskey (Yamazaki) that uses rice as part of the grain bill, and it was actually quite nice.
I've read there are oat-based whiskeys out there for the tasting, too...
