Chef Alton Brown wrote up some trivia about the history of egg nog at mental-floss. Although we tend to think of it as a medieval European recipe, it owes a lot of its popularity to the New World.
Egg-based drinks found new popularity in the American colonies, where nearly everyone had access to cows, chickens, and rum.
Nutritious and relatively stable, eggnog was our first health drink. If you ask me, sipping it is our patriotic duty.
But the best part is his personal recipe for homemade egg nog, plus tips for making it correctly. Follow it to the letter and you'll have nog with rum, cognac, and bourbon all together! Link