The document summarizes the history of three classic cocktails - the Gin Cocktail, Manhattan, and Singapore Sling. It provides the original recipes for each cocktail and explains how the modern versions differ significantly - they are sweeter, fruitier, and contain less of the original core ingredients like gin or vermouth. The document attributes the changes to shifts in liquor styles and tastes over time as well as a rise of fruity, novelty cocktails over the more sophisticated originals.