"Big St. Louis might be a reference to a boat/ship or a place in Charlottestown".

Perhaps...but "Big St. Louis is burnin down" might also be a misremembering of the line "East St Louis is burnin down".

And that "East St. Louis is burnin down" line demonstrates how Blues & other songs includes scattered references to historial events.

That line also may demostrate how historical references in songs are often forgotten or aren't recognized as historical markers by future singers and collectors of such songs.