Granville Stanley Hall was a pioneering American psychologist and educator who earned the first doctorate in psychology awarded in the United States of America at Harvard College in the nineteenth century. His interests focused on human life span development and evolutionary theory. Hall was the first president of the American Psychological Association and the first president of Clark University. A Review of General Psychology survey, published in 2002, ranked Hall as the 72nd most cited psychologist of the 20th century, in a tie with Lewis Terman. .

The American Psychological Association (APA) is the main professional organization of psychologists in the United States, and the largest psychological association in the world. It has over 157,000 members, including scientists, educators, clinicians, consultants, and students. It has 54 divisions, which function as interest groups for different subspecialties of psychology or topical areas. The APA has an annual budget of around $125 million.