Question

What enormous area of land was anchored to the South by the city of New Orleans?

Answer 1

The entire watershed of the Missouri and Mississippi Rivers, including the Ohio River Valley, Tennessee River Valley, Arkansas River Valley.

Explanation:

All the commerce west of the Appalachian Mountains flowed out through the port of New Orleans. The entire Northwest, territories of Western Pennsylvania, Ohio, Indianan, and Illiousis Most of the western southern states ,Kentucky , Tenenessee , Mississippi Louisiana , Arkansas and Texas.

The importance of New Orleans was why Thomas Jefferson felt the US had to purchase the port of New Orleans from the French.
The dependence of the US commerce was why Andrew Jackson defended New Orleans from the British in 1814. The conquest of New Orleans by the Union hurt the Confederacy.

Look at the map of the Louisiana Purchase to see about half of the land that was anchored by the Port of New Orleans.