The exposing of Standard Oil's Corruption
Tarbell used familiar muckraking tactics such as gaining the trust of several of Rockefeller's close associates and interviewing one of the companies founders, Frank Barstow. After months of research, she finally uncovered the crucial piece of evidence she needed. She discovered that Standard Oil had been rigging the railroad prices to decrease the value of it's competition until they were cheap enough to buy out.
Tarbell's exposé gave the thousands of American's who were upset with Standard Oil's business practices some validity. It also converted many of the public readers from McClure's magazine to a stance against Standard Oil and the idea of monopolization in any sector of business.