The earliest evidence of using occupations as a method of therapy can be found in ancient times. In c. 100 BCE, Greek physician Asclepiades initiated humane treatment of patients with mental illness using therapeutic baths, massage, exercise, and music. Later, the Roman Celsus prescribed music, travel, conversation and exercise to his patients. However by medieval times the concept of humane treatment of people considered to be insane was rare, if not nonexistent. (1)

In 18th century Europe, revolutionaries such as Philippe Pinel and Johann Christian Reil reformed the hospital system. Instead of the use of metal chains and restraint, their institutions utilized rigorous work and leisure activities in the late 18th century. Although it was thriving abroad, interest in the reform movement waxed and waned in the United States throughout the 19th century. At the turn of the 20th century, as physicians became increasingly interested in chronic disease, enthusiasm for the reform of the mental healthcare system was revived in the United States through work therapy. (1)

The health profession of occupational therapy was conceived in the early 1910s. The focus was on promoting health in “invalids.” Early professionals merged highly valued ideals, such as having a strong work ethic and the importance of crafting with one’s own hands with scientific and medical principles. Early opponents of this view considered wood carving and crafting by ill patients trivial. (1)

The emergence of occupational therapy challenged the views of mainstream scientific medicine. Instead of focusing on purely physical etiologies, they argued that a complex combination of social, economic, and biological reasons cause dysfunction. Principles and techniques were borrowed from many disciplines—including but not limited to nursing, psychiatry, rehabilitation, self-help, orthopedics, and social work —to enrich the profession’s scope. Between 1900 and 1930, the founders defined the realm of practice and developed theories of practice. In a short 20-year span, they successfully convinced the public and medical world of the value of occupational therapy and established standards for the profession. (1)

A substantial lack of primary sources of information has left today’s occupational therapists with many questions concerning the founders of the field. Information is collected from early training institutions and hospitals, professional writings of practitioners, World War I records from government agencies, newspaper articles, and personal testimonials. (1)

World War I forced the new profession to clarify its role in the medical domain and to standardize training and practice. In addition to clarifying its public image, OT also established clinics, workshops, and training schools nationwide. Due to the overwhelming number of wartime injuries, “reconstruction aides” (an umbrella term for physical therapists and occupational therapists) were recruited by the Surgeon General. Between 1917 and 1920, nearly 148,000 wounded men were placed in hospitals upon their return to the states. This number does not account for those wounded abroad. The success of the reconstruction aides, largely made up of women trying to “do their bit” to help with the war effort, was a great accomplishment. Post-war, however, there was a struggle to keep people in the profession. Emphasis was shifted from the altruistic war-time mentality to the financial, professional, and personal satisfaction that comes with being a therapist. To make the profession more appealing, practice was standardized, as was the curriculum. Entry and exit criteria were established, and AOTA advocated for steady employment, decent wages, and fair working conditions. Via these methods, occupational therapy sought and obtained medical legitimacy in the 1920s. (1)

References
(1) http://en.wikipedia.org/wiki/Occupational_therapy