Bourbon

Bourbon is the best-known and most-produced category of American whiskey and it charts its origins in the 18th century. Distilling had arrived on the continent 100 years earlier with colonists from Europe but was largely focussed on rum production until war with the British in 1776 disrupted the sugar trade. This saw Americans turn to domestic grains such as corn and rye, with whiskey produced predominantly from the former to become known most commonly as bourbon.

A category with strict regulation, bourbon whiskey by definition is required to be distilled within the United States of America, from a mash of at least 51% corn and aged in charred new American oak barrels. The most common variation, straight bourbon, has a minimum age requirement of 2 years. Known as American Standard Barrels (ASB), the casks are generally 200 litres in size however cooper's can also create ex-bourbon hogsheads by adding extra staves before refilling, increasing capacity to 250 litres.

The insistence upon single-use barrels in the ageing of bourbon became law in the 1930s and is believed to have been heavily lobbied for by cooper unions and the timber industry. Whatever the cause, the result was a bounty of available ex-bourbon barrels which were significantly cheaper for distillers to acquire than the traditionally used port and sherry casks of the past and imparted an entirely different flavour profile to their whiskies as well. Today, ex-bourbon casks remain the maturation staple of almost all whisky-producing nations outside of the US.