The development of the modern concept of mania is explored by a review and analysis of 28 psychiatric texts in English, French, and German published in Western Europe and North America from 1780 to 1900. From 1780 until the 1820s, mania was consistently viewed as a disorder of reasoning/judgment manifest by total insanity and/or the state of undifferentiated fury. For the next 30 years, the consensus shifted, and mania was understood to be largely a disorder of elevated mood. This concurrence of opinion broke down around 1860. For the remaining years of the 19th century, the mood-based model of mania competed for dominance with the view that mania arose primarily from accelerated mental processes and to a lesser degree that mania resulted from psychomotor excitation. While most authors advocated for one of these three positions, a number suggested that two or all three of these processes were central to the etiology of mania. Faculty psychology played an important role in these discussions, providing a framework within which to place the mental disturbance considered foundational to the manic syndrome. When the viewpoints shifted away from mania as a primary disorder of judgment, new approaches were needed to understand the emergence of grandiose delusions. Utilizing the concept of understandability, a number of authors suggested that manic delusions could arise directly from a euphoric mood. The history of mania shares some important similarities and differences with the history of melancholia during this same period. Both histories suggest that our major psychiatric categories evolved through a complex process involving both observations of symptoms, signs and course, and conceptual developments and a priori theories.