The process makes the product unique: Anchor Steam beer and only Anchor Steam beer is fermented in shallow pans and naturally carbonated. But no one really knows the origin of the name -- no steam is used to brew it.

With the wave of Teutonic immigrants to the United States in the mid-nineteenth century, German-style lager beer replaced ale as the brew of choice. But lager beer, fermented at about 45 degrees F and aged at near-freezing, required enormous quantities of ice, a product that was prohibitively expensive in gold-rush San Francisco. No one knows for sure what "steam beer" meant in those days. It was a nickname for draft beers that were brewed quickly and without ice. Anchor Brewing Co. bases its formula for Anchor Steam beer on what it has surmised about the old brew. It uses shallow-pan fermenters -- huge, open containers that spread and radiate the heat from fermentation, which takes place at 60 degrees to 70 degrees. The beer is then aged at 50 degrees, and 15% of newly fermented brew is added to the previous batch to "krausen," or to carbonate, the brew naturally. The best guess is that the name came from the result of the brewing method. Brewed and stored at a high temperature, the beer was extremely volatile, and when a bartender tapped a keg it would make a loud hissing sound -- like steam.

Today, as the only brewer using this method, Anchor Brewing's master brewer, Fritz Maytag, is convinced that Anchor alone can be called steam beer -- and he is willing to go to court to keep others from using the term.