Lincoln Steffens exposed corruption in business and politics through his journalism, making him a key figure of the Progressive Era.
Lincoln Steffens, a key figure in the Progressive Era, was considered a reformer because he exposed problems in business and politics through his investigative journalism. The Shame of the Cities was his notable work that criticized municipal corruption in many U.S. cities, contributing to the era's reform movements.
https://brainly.com/question/243885