What caused progressivism in the United States?

The causes of progressivism in the United States include urbanization, industrialization, corruption, and immigration. Between 1870 and 1900, the US saw a surge in population as more people flocked to urban centers. Many people sought factory jobs, and with those jobs came exploitation. For instance, employers hired children to work in deplorable conditions until progressive journalists known as muckrakers highlighted the plight of child workers. Child labor sparked an uproar from the public, which inevitably caused the government to ban child labor and establish labor laws. In addition, muckrakers wrote pieces exposing political corruption and other injustices.
The progressive movement was comprised of politicians, journalists, and intellectuals who contributed new ideas and pieces of legislation aimed at protecting workers and securing a more equitable society. Progressives encouraged citizens to participate in government through voting and protesting against corrupt leaders. Moreover, industrialization saw the rise of industry tycoons who held large concentrations of wealth and retained monopolies. In response, President Teddy Rosevelt enforced anti-trust laws to break up monopolies within certain industries.
https://www.britannica.com/event/Sherman-Antitrust-Act

https://www.britannica.com/topic/progressivism

https://www2.gwu.edu/~erpapers/teachinger/glossary/progressive-era.cfm