This thesis focuses on Ida M. Tarbell, one of the most influential literary figures of the late 19th and early 20th century in the United States. She has been recognized as the pioneer of investigative journalism and generally referred to as a muckraker. This study, however, will argue that she was primarily a historian. By putting her two significant historical works, Life of Lincoln and The History of the Standard Oil Company, into the center of analysis and by exploring her career in general, it will try to demonstrate Tarbell’s qualities as a historian and her contribution to the history discipline. In general terms, it aspires to explore Tarbell’s position in American literary, social and economic history.