I've been looking at the broadside ballads in the Bodleian Library collection. There are a number of copies of a C19th ballad called "The Indian Lass" which appears to have quite a few features in common with the Banks of Pontchartrain song, including the approxiamte location. The slant is slightly different, but it has the element of the stranger made welcome.

By the way, Planxty do my favourite version. What does definitive mean in this context?