In 1888, in the Investigation of Trusts conducted by Congress and by the State of New York, the Standard Oil Company was the chief subject for examination. In the state of Ohio, between 1882 and 1892, a constant warfare was waged against the Standard in the courts and the legislature, resulting in several volumes of testimony. The legislatures of many other states concerned themselves with it. This hostile legislation compelled the trust to separate into its component parts in 1892, but investigation did not cease; indeed, in the great industrial inquiry conducted by the Commission appointed by President McKinley, the Standard Oil Company was constantly under discussion, and hundreds of pages of testimony on it appear in the nineteen volumes of reports which the Commission submitted.
This mass of testimony—most, if not all, of it taken under oath—contained the different charters and agreements under which the Standard Oil Trust had operated, many contracts and agreements with railroads, with refineries, with pipe lines; and it contained the experiences in business from 1872 up to 1900 of multitudes of individuals. These experiences had exactly the quality of the personal reminiscences of actors in great events, with the additional value that they were given on the witness stand; and it was fair, therefore, to suppose that they were more cautious and exact in statement than are many writers of memoirs. These investigations, covering as they did all of the important steps in the development of the trust, included full accounts of the point of view of its officers in regard to that development, as well as their explanations of many of the operations over which controversy had arisen.
Aside from the great mass of sworn testimony accessible to the student, there was a large pamphlet literature dealing with different phases of the subject, as well as files of the numerous daily newspapers and monthly reviews, supported by the Oil Region, in the columns of which were to be found, not only statistics, but full reports of all controversies between oil men.
But the documentary sources were by no means all in print. The Standard Oil Trust and its constituent companies had figured in many civil suits, the testimony of which was in manuscript in the files of the courts where the suits were tried.