Final answer:
The fraternity began to open membership beyond 'Negroes' in alignment with the Civil Rights Movement, particularly after the Civil Rights Act of 1964 and the Voting Rights Act of 1965, which federally prohibited racial discrimination.
Step-by-step explanation:
To address the question of when the fraternity ceased restricting its membership exclusively to 'Negroes', we have to look at the broader context of civil rights history in the United States. Specifically, significant changes occurred in the mid-20th century. The sweep of the Civil Rights Movement led to the passage of legislation such as the Civil Rights Act of 1964 and the Voting Rights Act of 1965, which outlawed discrimination based on race and color among other factors. Within this context, African American fraternities and sororities that were part of the National Pan-Hellenic Council, such as Alpha Kappa Alpha, historically began as organizations for black college students in a time when they were excluded elsewhere. Over time, as segregation practices were legally abolished and societal norms progressed, these organizations became more inclusive. However, the specific point at which individual fraternities removed racial restrictions can vary and may require direct inquiry into their historical records.