Final answer:
In the 1950s, the U.S. shifted its focus to understanding race and ethnicity as social constructs instead of biological facts. This change was influenced by postmodernist thought and was reflected in the positions of social scientific associations. Local histories also began revealing a more complex picture of civil rights activism.
Step-by-step explanation:
In the 1950s, the United States began to focus more on the idea of race and ethnicity as social constructs rather than biological realities. This shift in perspective resulted in the rejection of biological explanations of race, which had been used in the past to justify practices such as discrimination and segregation. Insights from postmodernism played a key role in this transformation, redefining how race and ethnicity were understood within the American society. Scientific and social science organizations such as the American Association of Anthropologists and the American Sociological Association formally recognized that race is not biologically identifiable and that the previous racial categories were arbitrary. Furthermore, during this period, personal stories and local histories began to challenge the national narratives about race relations, shedding light on civil rights activism that occurred outside conventional time frames.