Sounds like you're further along than I thought.Pardon me if any of this is redundant to you... I'm just throwing out suggestions.You probably have already tried some. 1. There's a Jacksboro in TN and in TX.The TX one is up by Fort Worth.Have you checked the Henry's there?I'd hit the early 1900's censuses for both places - maybe via www.censuslinks.comand see if I could find some Henry families with young daughters. 2. I'm aware of the town of Henry, LA because of some Lees that lived there.It turns out that the Henry family in question was actually German or Dutch and was named Kattendid or something like that.They changed their name to Henry - something about anti-German sentiment at the time.Could this have happened to Granny's family? 3. There's got to be some kind of LA reference for old town names.Could there have once been a Jacksboro, that is now known as something else? 4. In particular in the targeted towns/counties, look for succession records.Someone's will might state that "I give to my daughter Mintrel blah blah blah...".
This is a toughie.It would have been a lot easier to find your grandfather in that timeframe than your grandmother - records were so much more complete for men.