Okay, found a good reference for this history. "Masters and Slaves in the House of the Lord: Race and Religion in the American South, 1740-1870, by John B. Boles, Editor", 1988.

Lots of church minutes showing the number of slaves in the churches across the South. I am going to have to get this one.

"A degree of closeness and an experience of real fellowship existed between black and white Baptist in biracial churches that, though recognized in the past, has not been adequately explored or analyzed. In a society of absolute inequality, local Baptist churches often provided for slaves and masters, blacks and whites, temporary interludes of symbolic equality, which found expression in various aspects of local congregational life."