Thanks so much for your post. I feel sure that this is my line - my 3G grandmother was Manerva Sigman (possibly Catherine Manerva Sigman). She married Robert Riddle and they named a son Barnett. According to the 1850 Rockcastle County census, she was born about 1821 or 1822 in North Carolina.
Any contacts you can suggest that would help me would be greatly appreciated.