The muckrakers were a group of American journalists who worked in the late 1800s and early 1900s. They were dedicated to exposing what they saw as negative conditions in American society.
During this time period, America was changing rapidly as immigrants flooded the country and businesses became bigger and more industrialized. These changes brought with them some very negative impacts. The muckrakers wanted to expose those problems (like slum housing, bad working conditions, and the excessive power of monopolies) so that people would demand change. By doing this, the muckrakers helped to build support for the Progressive movement.
The Muckrakers were investigative reporters who promoted social and political reforms by exposing corruption and urban problems. They were the leading critics of urban bosses and corporate robber barons. The rise of mass-circulation newspapers and magazines enabled muckrakers to reach a large audience. One of the Leading Muckrakers would be Upton Sinclair who wrote "The Jungle", exposing the abuses in the meatpacking industry. He also helped convince congress to pass the Meat inspection Act of 1906 and the Pure Food and Drug Act. Also Jacob Riis who was a journalist and a photographer working in NYC. His book "How the other half lives" provided an insight of human poverty experienced by immigrants.