Final answer:
A muckraker was a type of investigative journalist who exposed societal and political corruption during the Progressive Era, leading to significant reforms and public awareness of various issues.
Step-by-step explanation:
A muckraker refers to a type of journalist that emerged during the Progressive Era in the early 20th century in the United States, who investigated and published stories exposing corruption, social injustices, and unethical practices in business and politics. Despite the term initially being used in a derogatory sense, muckrakers played a crucial role in raising public awareness and prompting reforms. They dug deep into society's 'muck' and aimed to 'rake' it up for the public to see, hence the name 'muckraker.' Their work encompassed a variety of issues including child labor, poor working conditions, political corruption, and unsanitary conditions in the food industry which led to significant changes such as stricter labor laws and food safety regulations.