By 1850 the slaughterhouses of Cincinnati - 'Porkopolis' - had been refining the continuous production line for more than 20 years. Frederick Law Olmsted, the landscape and park designer, visited Cincinnati in the 1850s: "We entered an immense low-ceilinged room and followed a vista of dead swine upon their backs, their paws stretching mutely towards heaven. Amazed beyond all expectation at the celerity, we took out our watches and counted 35 seconds, from the moment when one hog touched the table until the next occupied its place. The numbers of blows required I regret we did not count."

Many a 19th century traveller stopped in Cincinnati or, later, Chicago to marvel at the efficiency and heartlessness of this unending,