Applied psychologists who were without PhDs or did not have academic affiliations were not, early in the 20th century, given full membership privileges at the scientifically oriented American Psychological Association (APA).
It had grown from the New York Association of Consulting Psychologists (NYACP), established in 1921 through the efforts of Leta Hollingworth and others.
A practitioner with a University of Pennsylvania PhD but no academic affiliation named David Mitchell became the NYACP's first president.
Later well-known presidents included Donald G. Paterson, Walter V. Bingham, Albert Poffenberger, and Carl Rogers.
During World War II, the U.S. military had a great need of professionals to treat soldiers with battle fatigue and other mental illnesses.