Invisible Churches (Slavery)
Invisible Churches among slaves in the United States were informal Christian groups where slaves listened to preachers that they chose without their master's knowledge. The Invisible Churches taught a different message from white controlled churches and did not emphasize obedience. Some slaves could not contact Invisible Churches and others did not agree with the Invisible Church message but many slaves were comforted by the Invisible Churches. 
The public churches formed often with controversy within and outside the communities. The 'invisible institution' existed often as a forbidden aspect; slaves might be members of both the independent black church groups or congregations that were racially mixed (Raboteau mentions that some such congregations might have far more slaves than masters in attendance), but also participate in worship gatherings at night in secret locations, risking severe punishment to do so.