For the time period leading up to the American revolution, the drink is a Bombo:
2 oz. rum
2 oz. water
1/2 teaspoon molasses
dusted with nutmeg
It's a simple, smooth drink and not bad. I can see how it could be the most popular drink in the period of no refrigeration or fresh fruit. I'm using Pyrat rum which probably makes it even a little sweeter than normal but that's how I like it. With the nutmeg, it almost tastes like a christmas cake. I will probably have to head down to Sun Liquor and have them make me one if they have the molasses and nutmeg.
Later, I really want to try and even older drink, the Flip, but I have no idea where I'll find a loggerhead and a fire to heat it with (wanting a new world drink rather than the European version heated in a pan), but it sounds good to me.