I've foud one reference the head of young Monroe here at Contemplator.com, a site that's been referenced in these threads before. According to the site:

Gerry's Rocks (Gerrish) are above The Forks, Maine and the events of the tune are related on a rock and tree on the Kennebec River. “Sagmor Town” is a corruption of Saginaw, which is probably a corruption of “Saguenay,” a river and site of an Indian settlement.

Still haven't found a version in which young Monroe pulls the key log out of the jam.

      - Mark