Final answer:
Ida Tarbell was the journalist who exposed the Standard Oil Company's monopolistic practices in her McClure's Magazine series, which led to the company's eventual breakup.
Step-by-step explanation:
The exposé of the oil industry between 1902 and 1904 that appeared in McClure's Magazine was conducted by Ida Tarbell, a talented researcher and journalist from Pennsylvania. Tarbell is most well-known for her painstaking and detailed investigation into the monopolistic practices of John D. Rockefeller's Standard Oil Company. Her work, which involved years of researching court filings and internal memos, was initially published as a series in a popular magazine and later in book form as The History of the Standard Oil Company. Recognized for its thoroughness and impact, Ida Tarbell's work played a pivotal role in the eventual breakup of the Standard Oil monopoly. Indeed, her efforts exemplify the muckraking journalism of the Progressive Era, though she personally preferred to be known as a historian.