Firts off, I do not have any direct information on Mary Polly Blair. I am responding to your confusion as the place of birth. Actually, all may be correct. I am attaching an URL that may give you some insight. It will give you an idea when the counties in TN were formed. Tennessee was initially two western most counties of NC. The same is similarly true for the relationship between VA and KY. There is also a strip of land across the top of TN that was or is part of KY or vice versa. New counties were created out others as the population moved west. see www.n2genealogy.com/tennessee/tn-maps.html