The statement best describes why progressives worked reform the meat packing industry in the early 1900s is "The industry used unsafe manufacturing practices."
Progressivism is the support for or advocacy of social reform. It is based on the idea of progress, which claims that advancements in science, technology, economic development and social organization are fundamental to the improvement of the human condition.
Before the turn of the 20th century, a major reform movement had emerged in the United States.