IN 1858, A BUSINESSMAN CALLING himself “Olfactorious” sent an angry missive to the New York Times. Following his doctor’s advice, he had moved out of the city in search of “sweet, uncontaminated air” in the countryside. But like many suburbanites, he still had to commute to the city for work, and he complained bitterly that his journey was dangerous given the stenches along his route. Each day, he passed a “festering” sewer, the source of “an effluvium sufficient to start the yellow fever.” Next came a milk factory with its “peculiar, penetrating, stump-tail odor,” and then a fat-rendering establishment that filled the air “with an odor exactly like roast mutton, only more so.” Thanks to the theory of miasma, which had a long and global history, Olfactorious feared that he would fall sick if he inhaled these foul smells.

Melanie Kiechle, a history professor at Virginia Tech and the author of Smell Detectives: An Olfactory History of 19th-Century America, 1840–1900, researches how Americans once tried to use their sense of smell to stay healthy. Until germ theory was widely accepted and viruses were discovered in the 1890s, Americans looked to the environment to understand the spread of disease. Nineteenth-century doctors blamed miasma, a noxious form of “bad air,” and worried about the poisonous fumes and putrid smells of America’s growing cities.

Back then, urban environments were olfactory nightmares: Chicago reeked of its slaughterhouses, New Orleans smelled like its gasworks, fertilizer factories dumped stinking heaps of waste in the middle of Manhattan, and animal carcasses rotted in the filthy canals of Providence, Rhode Island. For the first time in history, large numbers of Americans lived in overcrowded cities, many in poorly ventilated apartments, and killers such as cholera, tuberculosis, yellow fever, and typhus could strike at any moment, and often did. The campaign to eradicate foul odors and disinfect the air that urban dwellers breathed gave rise to a public health movement. Its founders took as an aphorism the words of a British health reformer: “All smell is disease.”