The Department of Terrestrial Magnetism, invariably called DTM and referred to briefly in the beginning as the Department of International Research in Terrestrial Magnetism, was the creation of Louis Agricola Bauer and for most of the time of his active participation it was the creature of his will. Bauer was born of German–American parents in Cincinnati in 1865. He completed a doctoral dissertation at Berlin in 1895 on the mathematical analysis of the secular variation of the Earth's magnetic field, and this thesis work so stimulated his interest that he established a scientific journal, Terrestrial Magnetism: An International Quarterly, in 1896 when he returned to the United States, the only periodical devoted specifically to geomagnetism, atmospheric electricity and related subjects.

Perhaps the greatest accomplishment of nineteenth-century physics was the creation of a theory that described accurately all of the observed phenomena of electricity and magnetism, a theory that predicted as its crowning achievement the existence of electromagnetic waves. By the end of the century this had given rise to a practical method for maritime communication over distances of hundreds of kilometers, the last of the century's practical applications that were rapidly transforming civilization: worldwide telegraph systems, cities linked by telephone, electric traction for railways and the replacement of dim oil lamps by brilliant electric lights. For all its triumphs, however, the theory left one particularly vexing question unexplained. There was nothing that provided even a clue for the origin of the Earth's magnetic field.