Regarding the theory that the "flag of true blue" in the penultimate line of the song is the "Bonnie Blue Flag" of the Confederacy, those lyrics were apparently first published in 1847, while (according to Wikipedia and other historical sites) the "Bonnie Blue Flag" was not used by the Confederacy until the early months of 1861. So maybe there's still hope for the two folks in the gumtree canoe. Of course, they were still in slave country, unless the song harks back to before the War of 1812 and they had floated all the way down to the Spanish territory of coastal Alabama.