Cocktail Society explains that the recipe for the Manhattan has gone through several variations. An early printed edition called for adding gum syrup and Absinthe to the mix; These were scrapped in 1900. The type of whiskey used in a Manhattan has been in flux too: Naturally Canadian whiskey was used during Prohibition, due to how easy it was to get compared to its then-illegal American or Irish counterparts. Bourbon was — and remains — a popular choice. But it’s rye whiskey that serves up the best Manhattan.
Whiskey serves as the base of the cocktail, with a ratio of whiskey to vermouth anywhere from a 50/50 split to whiskey doubling the vermouth, but this will vary depending on taste (via Bar Talk and Cocktails). With so few ingredients, no matter what your preferred mix the whiskey will really stand out — and Serious Eats states that rye does just that. Being a stronger drink than your typical Bourbon, rye compliments the Manhattan’s vermouth and bitters well while still maintaining its own presence. (The issue with Bourbon, the outlet explains, is that its flavor derives from a combination of corn and wheat, which don’t exactly marry well with the other two ingredients.) This is all a matter of taste, of course, but if you were never quite sold on the Manhattan, we suggest you rye it up the next time you’re out on the town.