This is a very interesting topic. I find it interesting that most dont realize that segregation in the south was law. Jehovah's Witnesses dont fight against the law of the land, unless it conflicts with their agenda. Obviously segregation did not affect the congregations in the south in that both a white and black congregation could exist, they could worship, and do field service without conflicting with local segregation laws.
In fact if one were to do the research I believe the "church" was the last of the institutions in the south to integrate. Most did not feel comfortable integrating in church, given their were other issues involved, including cultural & worship differences that had nothing to do with race relations.
Some commented regarding african-american witnesses not rising to the position to GB, until Sam Heard was appointed recently. It is true that and has been stated often that there were some who were qualified both african american, as well as those from africa. However, an appointment to the GB would require them to know English and live in Brooklyn (odd requirement indeed!). I have heard stories that brothers like Martin Poetzinger had difficulty learning English, and had he not been fluent, then his appointment would have been made null. There have been other qualified african-american brothers such as Thomas Banks and Henry Brisett, two traveling brothers, however I am not sure if either of them were alive when the GB was expanded in 1971. Since 1971, I am sure the number of qualified "anointed" african american brothers is quite small. I believe because of the "anointed" requirement, there werent many who would have qualified. However, there are brothers such as Leon Weaver and Ralph Walls who have been at Bethel for over 30 years, and because of their "non-anointed" status, arent ever considered for appointment to the GB. Heck, look at Max Larson (white), has been of the anointed for some time now, has been at Bethel, total organization man (minus the bushy eyebrows), has been at Bethel since the 50's and has not received an appointment. Trust me, I believe there are many factors in the selection process.
Recently I have heard a few african-american commentators say that though the civil rights movement pushed hard to remove segregation laws in the south. Today, many african-americans gravitate to one another, prefer to live only with other blacks and often refuse to integrate or associate with whites, lest they be called an uncle tom. Isnt that ironic, given all the struggles...