What style of beer was developed in the 19th century in California using warm fermentation with Lager yeast?

The style of beer that was developed in the 19th century in California using warm fermentation with lager yeast is Steam beer. This unique brewing method allowed brewers to produce a lager-style beer in the warmer climate of California, where traditional cold fermentation was not feasible.

Steam beer is characterized by its use of lager yeast strains, which typically ferment at cooler temperatures, and the warmer fermentation conditions that resulted in a distinctive flavor profile. The process created by early California brewers involved fermenting the lager yeast at higher temperatures, which contributed to the beer's fruity and estery notes, distinguishing it from typical lagers. Additionally, the high levels of carbonation and the use of Northern Brewer hops further define the characteristics of Steam beer.

While Lager is a broader category that encompasses many styles fermented with lager yeast, and Belgian Ale and Wheat beer have different fermentation techniques and flavor profiles, Steam beer specifically refers to the adaptation made in California that combines the warmer fermentation conditions with lager yeast, making it a unique product of that particular time and place.