The meat packing industry handles the slaughtering, processing, packaging, and distribution of animals such as cattle, pigs, sheep and other livestock. Poultry is not included. This greater part of the entire meat industry is primarily focused on producing meat for human consumption, but it also yields a variety of by-products including hides, feathers, dried blood, and, through the process of rendering, fat such as tallow and protein meals such as meat & bone meal.
In the U.S. and some other countries, the facility where the meat packing is done is called a slaughterhouse, packinghouse or a meat packing plant; in New Zealand, where most of the products are exported, it is called a freezing works. An abattoir is a place where animals are slaughtered for food.
The meat packing industry grew with the construction of the railroads and methods of refrigeration for meat preservation. Railroads made possible the transport of stock to central points for processing, and the transport of products.
Before the Civil War, the meat industry was localized, with nearby farmers providing beef and hogs for local butchers to serve the local market. Large Army contracts during the war attracted entrepreneurs with a vision for building much larger markets. The 1865–1873 era provided five factors that nationalized the industry:
- The rapid growth of cities provided a lucrative new market for fresh meat.
- The emergence of large-scale ranching, the role of the railroads, refrigeration, and entrepreneurial skills.
- Cattle ranching on a large-scale move to the Great Plains, from Texas northward.
- Overland cattle drives moved large herds to the railheads in Kansas, where cattle cars brought live animals eastward.
- Abilene, Kansas, became the chief railhead, shipping 35,000 cattle a year, mostly to Kansas City, Milwaukee and Chicago.
In Milwaukee, Philip Armour, an ambitious entrepreneur from New York who made his fortune in Army contracts during the war, partnered with Jacob Plankinton to build a highly efficient stockyard that serviced the upper Midwest. Chicago built the famous Union Stockyards in 1865 on 345 swampy acres to the south of downtown. Armour opened the Chicago plant, as did Nelson Morris, another wartime contractor. Cincinnati and Buffalo, both with good water and rail service, also opened stockyards. Perhaps most energetic entrepreneur was Gustavus Franklin Swift, the Yankee who operated out of Boston and moved to Chicago in 1875, specializing in long distance refrigerated meat shipments to eastern cities. 
A practical refrigerated (ice cooled) rail car was introduced in 1881. This made it possible to ship cattle and hog carcasses, which weighed only 40% as much as live animals; the entire national market, served by the railroads, was opened up, as well as transatlantic markets using refrigerated ships. Swift developed an integrated network of cattle procurement, slaughtering, meat-packing and shipping meat to market. Up to that time cattle were driven great distances to railroad shipping points, causing the cattle to lose considerable weight. Swift developed a large business, which grew in size with the entry of several competitors. 
The Pure Food and Drug Act of 1906 was the first of a series of legislation that led to the establishment of the Food and Drug Administration (FDA). Another such act passed the same year was the Federal Meat Inspection Act. The new laws helped the large packers, and hurt small operations that lacked economy of scale or quality controls. 
Historian William Cronon concludes:
- Because of the Chicago packers, ranchers in Wyoming and feedlot farmers in Iowa regularly found a reliable market for their animals, and on average received better prices for the animals they sold there. At the same time and for the same reason, Americans of all classes found a greater variety of more and better meats on their tables, purchased on average at lower prices than ever before. Seen in this light, the packers' "rigid system of economy" seemed a very good thing indeed. 
In the early part of the 19th century, they used the most recent immigrants and migrants as strikebreakers in labor actions taken by other workers, also usually immigrants or early descendants. The publication of the Upton Sinclair novel The Jungle in the U.S. in 1906, shocked the public with the poor working conditions and unsanitary practices in meat packing plants in the United States, specifically Chicago.
Meat packing plants, like many industries in the early 20th century, were known to overwork their employees, failed to maintain adequate safety measures, and actively fought unionization. Public pressure to U.S. Congress led to the passage of the Meat Inspection Act and Pure Food and Drug Act, both passed in 1906 on the same day to ensure better regulations of the meat packing industry as well as better treatment of its employees working there. Before the Meat Inspection Act and the Pure Food and Drug Act, workers were exposed to dangerous chemicals, sharp machinery, and horrible injuries.
In the 1920s and early 1930s, workers achieved unionization under the CIO's United Packinghouse Workers of America (UPWA). An interracial committee led the organizing in Chicago, where the majority of workers in the industry were black, and other major cities, such as Omaha, Nebraska, where they were an important minority in the industry. UPWA workers made important gains in wages, hours and benefits. In 1957 the stockyards and meat packing employed half the workers of Omaha. The union supported a progressive agenda, including the Civil Rights Movement of the 1960s. While the work was still difficult, for a few decades workers achieved blue-collar, middle-class lives from it.
Though the meat packing industry has made many improvements since the early 1900s, extensive changes in the industry since the late 20th century have caused new labor issues to arise. Today, the rate of injury in the meat packing industry is three times that of private industry overall, and meat packing was noted by Human Rights Watch as being "the most dangerous factory job in America". The meatpacking industry continues to employ many immigrant laborers, including some who are undocumented workers. In the early 20th century the workers were immigrants from eastern and southern Europe, and black migrants from the South. Today many are Hispanic, from Mexico, Central and South America. Many are from Peru, leading to the formation of a large Peruvian community. The more isolated areas in which the plants are located put workers at greater risk due to their limited ability to organize and to seek redress for work-related injuries.   
The industry after 1945 closed its stockyards in big cities like Chicago and moved operations to small towns close to cattle ranches, especially in Iowa, Nebraska and Colorado. Historically, besides Cincinnati, Chicago and Omaha, the other major meat packing cities had been South St. Paul, Minnesota; East St. Louis, Illinois; Dubuque, Iowa; Kansas City, Missouri; Austin, Minnesota; Sioux Falls, South Dakota; and Sioux City, Iowa.
Mid-century restructuring by the industry of the stockyards, slaughterhouses and meat packing led to relocating facilities closer to cattle feedlots and swine production facilities, to more rural areas, as transportation shifted from rail to truck. It has been difficult for labor to organize in such locations. In addition, the number of jobs fell sharply due to technology and other changes. Wages fell during the latter part of the 20th century, and eventually, both Chicago (in 1971) and Omaha (in 1999) closed their stockyards. The work force increasingly relied on recent migrants from Mexico.
Argentina had the natural resources and human talent to build a world-class meat-packing industry. However its success in reaching European markets was limited by the poor quality control in the production of their meat and the general inferiority of frozen meat to the chilled meat exported by the United States and Australia, By 1900, the Argentine government encouraged investment in the industry to improve quality. The British dominated the world shipping industry, and began fitting their ships for cold air containers, and built new refrigerated steamers. When the Argentine industry finally secured a large slice of the British market, Pateros and trade restrictions limited its penetration of the Continent. 
Meat in China moved from a minor specialty commodity to a major factor in the food supply in the late 20th century thanks to the rapid emergence of a middle-class with upscale tastes and plenty of money. It was a transition from a small ration of meat only for urban citizens to the world's largest meat-producer; it was a movement from a handful of processing facilities in major cities to thousands of modern meat packing and processing plants throughout the country. With the rapid growth of a middle-class with spending money, 
At 1900 the dominating meat packers were: 
In the 1990s the Big Three were: 
- Smithfield Foods
- Tyson Foods
- JBS USA
- Cargill Meat Solutions
Outside the United States:
- Teys Australia
- JBS S.A. (Brazil)
- BRF S.A. (Brazil)
- Charoen Pokphand Group (Thailand)
- Imperial Cold Storage and Supply Company (South Africa)
- Maple Leaf Foods (Canada)
- Schneider Foods (Canada)
- AFFCO Holdings (New Zealand)
- Continuous inspection
- Labor rights in American meatpacking industry
- Union Stock Yards, Chicago
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