Final answer:
The muckrakers were journalists and writers who reported on the hazardous conditions in factories and cities during the Progressive era.
Step-by-step explanation:
The muckrakers, a group of journalists and writers, reported on the hazardous conditions in factories and cities during the Progressive era. They exposed problems in American society through their articles and books, bringing attention to issues such as poor working conditions, low pay, and corruption. Some well-known muckrakers include Jacob Riis, Ida Tarbell, Lincoln Steffens, and Ray Stannard Baker.