Still a boy, Snow was apprenticed to William Hardcastle, a surgeon apothecary in Newcastle upon Tyne, at the age of fourteen. Four years later, the cholera epidemic of 1831 struck, and Snow found himself attending to the affected miners at Killingworth colliery. It was an experience he clearly took to heart, and his efforts to understand the disease would consume a large proportion of his professional life. However, his first specialism was as an anaesthetist. An early proponent of the use of ether and chloroform, from 1847, he published at least eighteen papers on the subject before 1851, and administered chloroform to Queen Victoria during the births of Prince Leopold (1853) and Princess Beatrice (1857).
Snow was one of the first members of the Epidemiological Society, founded in 1850. He had explored his theory that cholera was a waterborne infection as early as 1849 in On the Mode of Communication of Cholera, however it wasn’t until he had obtained statistical evidence from the 1854 outbreak of cholera in Broad Street, London, that it gained traction. Using a list of deaths obtained from the General Register Office he mapped the location of each death, illustrating clearly that the majority of victims obtained their water from the Broad Street pump. In a dramatic, but necessary gesture, the handle of the pump was removed.
An abstemious personality as a young adult, Snow was a vegetarian, and a staunch member of several temperance societies. However, his health began to deteriorate during the mid-1840s, and so on the advice of well-wishing friends and colleagues he resumed the consumption of both meat and drink. Nevertheless, he died of a stroke, brought on by advance renal disease, in the summer of 1858.