Final answer:
Muckraking journalists of the Progressive Era were primarily known for exposing corruption and societal problems in the U.S., which led to public awareness and legislative reforms in the early 20th century.
Step-by-step explanation:
The muckraking journalists of the Progressive Era were chiefly recognized for exposing corruption and societal issues in the United States. They played an instrumental role in highlighting the many problems plaguing the nation, including corrupt politics, poor working and living conditions, and the power held by big businesses. This form of journalism, often found in outlets like McClure's magazine, was influential in spurring the public and policymakers to pursue reforms and led to significant changes, such as the Pure Food and Drug Act.
Rather than focusing on sensationalism, muckrakers like Upton Sinclair, backed by the principles of Progressivism, aimed to alert the public and push for legislative change through their fact-based and in-depth reporting. Their work was a catalyst for the wider Progressive movement, which strived for improving democracy, efficiency, and social justice within America during the early 20th century.