20ml Orange Liqueur
20ml Lemon juice
It is believe that the sidecar was named after a captain that was known for being driven between a bar where the cocktail was created. Although, it isn’t stated where or what the bar is. It is commonly accepted to be Harry’s New York Bar in Paris.
It is believed that created by Pat MacGarry at Bucks Club London and Harry MacElhone popularised the drink. MacElhone published the recipe in his 1922 book ABC of Cocktails and credits MacGarry, but later editions he credits himself.
Info from: http://www.diffordsguide.com/encyclopedia/2014-08-26/506/cocktails/sidecar-cocktail