Went to the Stax records museum in Memphis a while back. First room is a reconstructed church with video clips of gospel singers from the 30's.
Very cool! However, IIRC, the Chess label is when gospel turned into R&B and R&R. Early artists were Muddy Waters, Howlin Wolf, Little Walker, Bo Diddley, Etta James, Willie Dixon, and Chuck Berry for a short time. There's a movie, "Cadillac Records" based on the Chess label. The Stones recorded there once or twice.