London
Such fogs were prevalent in UK cities, especially London where the smoke from millions of chimneys combined with the mists and fogs of the Thames valley. The result was commonly known as a London particular or London fog, which then, in a reversal of the idiom, became the name for a thick pea and ham soup.[1]
An 1871 New York Times article refers to "London, particularly, where the population are periodically submerged in a fog of the consistency of pea soup..." The fogs caused large numbers of deaths from respiratory problems.[2]