Regrettably, I had to cut down your question to focusing only on the setting in Sinclair's work. I think that the setting is essential in bringing out the thematic development of the work. The stockyards and stockyard life is what resonated strongly with Americans during the Progressive time period. The element of "Muckracking" journalism present comes from these honest depictions of life in American urban centers, something that was not either acknowledged or not wished to be acknowledged. At the same time, the setting of factory life where there was no regulated or standardized practice and what that actually entails were major elements that motivated Americans to believe that a change was needed. Such attention to detail can also resonate with the reader of today, demonstrating that the settings evoked transcend time:
Modern readers can relate to the dehumanizing effects of boring, repetitive assembly-line labor and of employers who put profits before the health of their workers.
Sinclair's settings bring to light the conditions in which millions of people in America were living and dying. Sinclair's attention to setting details helped to create a vivid picture of an industrial and capitalist setting that has veered off the course and become one in needed of absolute change and transformation.