Vomiting. Diarrhea. Dehydration. Death. Confusion. In 1832, the arrival of cholera in the United States created widespread panic throughout the country. For the rest of the century, epidemics swept through American cities and towns like wildfire, killing thousands. Physicians of all stripes offered conflicting answers to the cholera puzzle, ineffectively responding with opiates, bleeding, quarantines, and all manner of remedies, before the identity of the dreaded infection was consolidated under the germ theory of disease some sixty years later. These cholera outbreaks raised fundamental questions about medical knowledge and its legitimacy, giving fuel to alternative medical sects that used the confusion of the epidemic to challenge both medical orthodoxy and the authority of the still-new American Medical Association. In Knowledge in the Time of Cholera, Owen Whooley tells us the story of those dark days, centering his narrative on rivalries between medical and homeopathic practitioners and bringing to life the battle to control public understanding of disease, professional power, and democratic governance in nineteenth-century America.