The person who investigated and reported John D. Rockefeller's corrupt business practices at Standard Oil was Ida Tarbell.
Ida Minerva Tarbell was an American professor, writer and journalist, considered one of the main "muckrakers" of the Progressive Era of the late 19th and early 20th century and a pioneer of investigative journalism.
She is known for her research on John D. Rockefeller and the Standard Oil Company, published in series by McClure's Magazine from 1902 to 1904; his investigations exposed the unfair monopolistic practices practiced by the company until the Supreme Court of the United States decided to dissolve the monopoly.
His 19 journalistic articles were compiled in a book she published in 1904 under the name of The History of the Standard Oil Company. In 1999, the University of New York cataloged her research as number 5 in a list of the 100 best works of American journalism of the 20th century.
