Upton Sinclair was called a "muckraker." How did Sinclair "muckrake" for social reform?
The "muckrakers" were a group of investigative journalists who dedicated themselves to uncovering social ills during the late 19th and early 20th centuries in the US.
They were give their name by Theodore Roosevelt, who meant it pejoratively. The name refers to people who rake out the soiled straw and bedding from a horse's stall.
Sinclair is best known for his book "The Jungle," in which he describes (in a fictional account that was closely based on the truth) conditions in the meatpacking industry of Chicago. He documents poor working conditions and really disgusting things that were done to meat that later became food.
The work of Sinclair and other muckrakers helped lead to many reform laws passed during the Progressive Era.
By dishing out what was wrong in society, specifically on government corruption or in business, a group of journalists were eventually called "muckrakers".
Sinclair wrote The Jungle, The Brass Check, in which the meatpacking industry and the "free press" were discussed respectively.
As mentioned above, this ultimately led to the reform of many laws.