In a Gibson cocktail, what traditional garnish distinguishes it from a classic Martini?

In a Gibson cocktail, a cocktail onion is the traditional garnish that distinguishes it from a classic Martini.

The Gibson is a mixed drink made with gin and dry vermouth, generally prepared in the same broad style as a Martini. Its defining visual and flavor detail is the small pickled onion placed in the glass. The onion adds a savory, gently acidic note to the otherwise spirit-forward drink.

The drink’s exact origin is disputed. Stories connect it with the early twentieth century and with a San Francisco businessman or diplomat named Charles Dana Gibson, but no single origin account is universally accepted. The name therefore has a clearer cocktail identity than a firmly documented creator.

A lemon twist or green olive can garnish a Martini, but neither is the traditional Gibson garnish. Recipes may vary in gin-to-vermouth ratio, and some modern bars offer vodka versions, yet the cocktail onion remains the key identifying feature. It is usually served chilled in a cocktail glass, often after stirring the gin and vermouth with ice.