What is the Reinheitsgebot?
"Furthermore, we wish to emphasize that in future in all cities, markets and in the country, the only ingredients used for the brewing of beer must be Barley, Hops and Water. Whosoever knowingly disregards or transgresses upon this ordinance, shall be punished by the Court authorities' confiscating such barrels of beer, without fail." -- The Reinheitsgebot, April 23, 1516
In English, Reinheitsgebot roughly translates to the German Beer Purity Law, which is a hell of a lot easier to say. Signed by the Bavarian co-rulers Duke Wilhelm IV and Duke Ludwig X into law on April 23rd, 1516, it stipulated that beer, by law, was only to be made with three ingredients: barley, hops, and water. Later, yeast was added to the list when its role in fermentation was discovered, and other ingredients were added still later, such as sugar in top fermenting beers. Still, the list was narrow.