Astonishing, True but Legendary Pioneer Adventure of the New River Region: "Follow the River" by James Alexander Thom
The real adventure begins when the French trader takes several white captives and a few Shawnee guards back across the Ohio to a make salt at Big Bone Lick in Northern Kentucky. The white captives, mostly women, are forced to do the hard labor of boiling salty water to produce the salt. No one has ever escaped from the salt lick, so the Shawnee are loose with security; Mary and another woman captive are able to walk away at the end of a hard day making salt in October.
(In order to make her escape, she is forced to abandon her new baby to the care of a young squaw, mistress of one of the French traders.)
The author says he researched his book by retracing on foot the route taken by the two women. He had tents and proper equipment for the ~1,000 mile hike, but the pioneer ladies did not. Neither did they have a good supply of food or weapons. In aching detail, day by day, he tells of their likely experiences, severe ordeals with cold, hunger and terror. Historically, we know they made it back alive; the fictional re-imagining is a page-turner. I loved this book.