Upton Sinclair and Ida Tarbell are both considered muckrackers.
Muchrackers are journalists who dig for scandals and dirt and exposed the facts to the public.
Upton Sinclair was an American writer who won a Pulitzer. He was famous for his novel "The Jungle", which exposed sanitary conditions and labor workforce in the meatpacking industry. Another famous novel was "The Brass check" where he talked about american journalism and yellow journalism and the free press.
Ida Tarbell was one of the pioneers in investigative journalism. She was well-known for taking complex subjects—the oil industry, tariffs, labor practices—and breaking them down into informative and easy to understand articles.