The Progressive movement can be defined as a reform movement that convulsed the nation at the dawn of the 20th century. Those that called themselves “progressives” sought to address the evils they saw besieging America, such as monopoly, corruption, inefficiency, and social justice.
They made the first comprehensive effort to solve the problems that arose with the emergence of a modern urban and industrial society. The issue they were addressing was that the US population nearly doubled between 1870 and 1900, accompanied by urbanization and immigration increasing at rapid rates. Plus, the American economy saw a shift from small scale manufacturing and commerce to large scale factory production.
During this period, an accompanying event was that the growth of national corporations from 1863 to 1899 that saw manufacturing production rise by more than 800% in the United States. That growth generated profound economic and social ills that challenged the United States in the eyes of those progressives.
The people that called themselves progressives were a diverse array of reformers; they were insurgent Republican officeholders, disaffected Democrats, journalists, academics, social workers, and other activists, including President Teddy Roosevelt, followed later by Presidents Taft and Wilson. The fact is many progressives viewed themselves as principled reformers at a critical juncture of American history.
Above all else, the progressives sought to come to terms with the extreme concentration of wealth among a tiny elite and the enormous economic and political power of the giant trusts, which they saw as uncontrolled and irresponsible. For them, the time was right for social ills to be addressed because they believed in progress, i.e., that life could be made better for everyone, not just an elite few.