The meat packing industry was very packed and it was very unsanitary because people would always come into work sick and not leave work.
Meat was usually left in big rooms with little cooling and would get spoiled/rotten very quickly but it will still be put into the hoppers to be made into meat.
Many political cartoonist made cartoons about how people sold bad meat and people knew but there was nothing they could do about it.
Almost nothing that went into the meat was ever checked or filtered for anything unhealthy or not actual meat.
The workers at the factories weren't treated any better than the slaughtered animals.
"All of this might seem diabolical, but the saloon-keeper was in nowise to blame for it. He was in the same plight as the manufacturer who has to adulterate and misrepresent his product. If he does not, some one else will."