Final answer:
Muckrakers were journalists who exposed widespread issues in American society, leading the public to demand government action, which sparked the passage of reform legislation during the Progressive Era.
Step-by-step explanation:
The work of the muckrakers played a crucial role in the Progressive Era by exposing corruption, societal problems, and prompting public outcry for reform. Muckrakers like Upton Sinclair and the journalists at McClure's magazine conducted thorough investigations into political and corporate misconduct. Their reports on issues such as child labor, unsanitary living and working conditions, and corruption within the political sphere captured the attention of the American public who, in turn, pressured the government for change. The muckrakers illuminated the need for government intervention, thus inspiring legislation such as the Pure Food and Drug Act among other reforms. This civic engagement, sparked by muckrakers' articles and books, showed that a well-informed public can indeed influence political action and lead to the betterment of society. President Roosevelt's view of muckrakers as both crucial yet obsessive highlights the duality in their role as instigators of reform.