Re: QUERY: "Prospectus" Maps
I'm by no means an expert on this material, but what you describe sounds like what they call "Plan Book Plans" at the notarial archives in New Orleans. There aren't a lot of examples of them online, but a few pages into the the first item here: http://www.orleanscivilclerk.com/ADVS.html there are some examples.
Adam Cox
MS Geography/MLIS student at Louisiana State University
Geospatial Developer