According to Robert Vermeire's 1922 Cocktails: How to Mix Them, the sidecar was invented by the celebrated bartender MacGarry of London's Buck's Club. More Classic Cocktails
Moisten half of the outer rim of a chilled coupe with the lemon wedge and coat lightly with sugar. Fill a cocktail shaker with ice. Add all of the remaining ingredients and shake well. Strain into the coupe.