Root beer, like the one we know and love today, was first commercially sold as an extract in the 1880s. You would buy the root beer extract (which was primarily made from sassafras), then mix it at home with water, sugar, and yeast. People loved it so much that the company behind the extract, Charles E. Hires Company, began selling root beer in bottles in 1893.
After a few years, more root beer manufacturers started popping up around the U.S., like Barq's, A & W, Dad's, and Mug Root Beer. All the root beers were basically made up of the same ingredients: either sassafras or sarsaparilla, licorice root, ginger, mint, cinnamon, and vanilla.
Root beer experienced a real boom during Prohibition when Americans couldn't buy real beer, so they turned to root beer as an alternative.
The ingredients in root beer pretty much stayed the same until 1976 when the Food and Drug Administration (FDA) banned the use of sassafras in food. The FDA discovered that the chemical found in sassafras, called safrole, caused cancer in rats — so sassafras is now considered carcinogenic.
That meant root beer manufacturers had to find a new main ingredient for their sodas: enter wintergreen. The wintergreen leaf was always an ingredient in root beer, but with sassafras gone, it took the front seat as the main flavor.
