Today, lager beers represent the comfort zone for most American beer drinkers, and a stereotyped monolith for many craft breweries to rebel against. But 170 years ago, lagers were both the outsider and the trendsetter. Their arrival caused ongoing debates over what beer was, what it should be, and the role alcohol ought to play in American social life, to take a sharp turn. This debate was anchored in beliefs about beer and public health that were simultaneously centuries old, and ever-evolving.