On this day in 1866 - Root beer was first prepared commercially.:

Root beer is a fermented beverage made from a combination of vanilla, cherry tree bark, licorice root, sarsaparilla root, sassafras root bark, nutmeg, anise, and molasses among other ingredients. Many local brands of root beer exist, and homemade root beer is made from concentrate or (rarely) from actual roots. The drink gets its name from its unique texture. Like alcoholic beer, root beer has a thick and foamy head when poured.

Root beer is a uniquely North American beverage, constituting about 3% of the American soft drink market.