Rye whiskey was widely prevalent before Prohibition took hold of America, for it was a hardy grain that could be grown without too much difficulty. The main difference from Bourbon is the mash bill. The mash bill is the list of grains used for distillation and, in America, rye whiskey is distilled from a minimum of 51% rye alongside barley, wheat and corn. It is the raw ingredient, the rye, that proffers the unique flavour profile; a savoury, spiciness.
Rye whiskey was the original cocktail spirit, when the first manhattans were stirred in pre-Prohibition era America. Canadian whisky is often referred to as rye whisky, though the mash bill need not contain any rye for it to be Canadian whisky. Historically, Canadian whisky was largely based upon rye, though lawfully in Canada whiskies may be referred to as ‘Canadian Whisky, ‘Rye Whisky’ or ‘Canadian Rye Whisky’ regardless of the rye content.
For some time, rye whiskey was largely out of fashion, but there has been a great resurgence recently, with premium brands, including Old Rip Van Winkle and Sazerac, producing wonderful spirits.