This article examines aspects of the psychology of adjustment from the late 19 th century to the end of the 1930s. Adjustment psychology influenced many aspects of American culture during this era. This historical account begins with American psychologists seeking to make psychology a natural science based on Darwinian theory. As applied science, adjustment psychology is exemplified here by its influence on psychiatry and mental hygiene. Adjustment psychology promised a science-based solution for the suffering attributed to chaos resulting from a rapidly changing society that was characterized by such unsettling factors as immigration, unpredictable economic factors, and rapid changes in technology. To represent this context, the history of adjustment psychology is discussed in terms of social engineering.