[DiogenesLamp]

Can you enlighten me on how the Shipping Act of 1817 caused a northern monopoly on hauling southern goods?

With a bunch of searching, I can find the relevant discussions about this for you, and I will look around for them, but i'm not going to be in a hurry about it. I think the matter was discussed quite a lot in that long thread, the link to which I have already posted for you.

I can tell you this much from memory. Federal payments to Northern Shipping companies for carrying the US Mail, gave them a competitive advantage against shippers located anywhere else.

[BroJoeK]

DiogenesLamp: "I can tell you this much from memory.
Federal payments to Northern Shipping companies for carrying the US Mail, gave them a competitive advantage against shippers located anywhere else."

Effecting only a handful of specialized ships out of the many hundreds required for US export/import trade.
The real reason Southern ship-building declined after 1800 was very likely the introduction of steam power and other heavy metal components which were not at the time produced in the South.

USS John Adams built in Charleston SC, launched 1799:

SS Planter steamboat carrying cotton, built in Charleston SC, launched 1860: