Final answer:
In 1948, over 50% of American physicians were members of the American Medical Association (AMA), which was known for its exclusionary practices and led to the creation of the National Medical Association.
Step-by-step explanation:
In 1948, over 50% of American physicians belonged to the American Medical Association (AMA). At the time, the AMA was and continues to be a prestigious professional group for physicians in the United States, it was also known for its exclusionary practices, particularly against Black physicians, which led to the formation of the National Medical Association in 1895. This separation within the medical community reflected broader societal issues of segregation and discrimination during that time period.