Easy to make and refreshingly bitter, the Negroni is said to have been invented in Florence by the dauntless Italian Count Camillo Negroni in the early 20th century. While at Bar Casoni in Florence, he demanded that the bartender strengthen his favorite cocktail, the Americano, by replacing the usual soda water with gin. To further differentiate the drink, the bartender also employed an orange peel rather than the typical lemon peel.
It’s a widely accepted tale, and one that is documented in “Sulle Tracce del Conte: La Vera Storia del Cocktail Negroni,” which was written by Lucca Picchi, the head bartender at Caffe Rivoire in Florence, Italy, and translates to “In the Footsteps of the Count: The True Story of the Negroni Cocktail.” The count’s fateful substitution resulted in one of the most popular stirred drinks in history, as the Negroni sits next to the Martini and Manhattan in the pantheon of classics. It also launched a thousand riffs, and today the Negroni can be found in myriad iterations at restaurants and cocktail bars around the world.
Few cocktails have encouraged more frenzied experimentation than the beloved Negroni during the course of its 100-year history. Its one-to-one-to-one recipe of gin, Campari and sweet vermouth has become the platform on which generations of drink mixers have left their thumbprint. Sub bourbon for gin, and you’ve got the Boulevardier, a great cocktail in its own right. Try rum or mezcal in the same equal parts configuration with Campari and sweet vermouth, and you get far different yet equally balanced and impressive drinks.

Référence :
https://www.liquor.com/recipes/negroni/

Référence :

https://www.diffordsguide.com/g/1078/negroni-cocktail/negroni-story