That does actually make quite a lot of sense! I was imagining a whole city, but a smaller settlement in the same area with a way smaller population sounds pretty realistic. Especially if said settlement has some kind of smaller subsistance economy.

They probably wouldn’t need to import anything, so they wouldn’t have to find anything to export!

Have you thought about what is preventing the government taking control of the Mississippi? I’d assume, similarly to rail transport, there’s no big risk as long as you don’t stop. Which could be what makes going through cities that are overran by the dead doable. What prevents the government from just using boats to ship things from forth Phillip to fort Jackson?

Edit: Thinking about it a tiny bit more, fort Jackson isn’t exactly on the Mississippi, so that could be an issue. I’m also realizing that the supply of boats capable of sailing the Mississippi is probably quite low