I found this recipe on liquor.com.

Equal parts of gin, Campari, and sweet vermouth⁣
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This drink started in Florence Italy in 1919. Count Negroni asked the bartender to beef-up his favorite cocktail, the Americano, by replacing the soda water with gin. Ta-da! New drink.⁣
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Besides having a cocktail named after him, Count Negroni traveled the US for a while, living the life of a cowboy.⁣ 🥃 🇺🇸 🤠 🇮🇹 ⁣
It is delicious. I’m so glad I’ve added Campari to my bar! The rich flavors blend together very well – gin, plus the bitter and the sweet.⁣