score:6
The answer is in the meat-packing industry and the development of a practical refrigerated boxcar, also known as the reefer. This permitted livestock ranched in the West to be slaughtered nearer the cattle ranges, and shipped back east with little spoilage - before, livestock were shipped live to local slaughter-houses in the East, who distributed the meat to local butchers. The problem with this arrangement is that the animals lost weight or even died outright during the stressful journey, and needed to be fed, watered and exercised along the way, so the quality of meat was not the best, and expensive, to boot. Before the advent of the reefer, only preserved meat products, like barreled (pickled) pork and cured sausage, could be shipped. The reefer permitted raw meat rather than the animal or processed meat-products to be shipped to wholesalers in places like Boston and Philadelphia from industrial-scale slaughter houses out west, in regional rail hubs like Kansas City and Chicago.
The first practical reefer car was designed by Andrew Chase at the behest of Gustavus Swift, a Chicago meat packer magnate. They were well insulated, and had a large compartment of ice set above the cargo compartment, allowing the chill air to circulate over the contents. Swift used these cars to create the Swift Refrigerated Line railroad in 1880, and began shipping beef to Boston, moving over 3,000 carcasses a week by the end of its first year in business.