Many of America’s most powerful and wealthy cities got there in part because of their status as major centers of trade (New York and Boston for example)
Now one would think that being a city at the mouth of the Mississippi, the heart of so much trade, would be rich from all that commerce.
But the city and the state are (compared to the rest of the country) rather poor. What gives?
I'm going to mostly talk about the US Antebellum era, because the Civil War, Reconstruction, and late 19th century industrialization and beyond are different balls of wax.
One thing to keep in mind is that while we can just say New York, New Orleans and Boston are "port cities", they aren't really interchangeably so - there are some big differences in terms of nature/geography/climate (what would feed into the "land" factor of production), and some major differences in how human capital developed between these regions.
So first one thing to keep in mind is that especially in the 19th century, climate was very different between the two regions (New Orleans and New York/Boston). This is less so today with climate change and with air conditioning, but you'd get even more pronounced differences then. It wasn't unknown for New York and Boston harbors to freeze in the winter, while New Orleans was resolutely subtropical and swampy. This also meant that while diseases like malaria and yellow fever weren't unknown in New York or Boston, they were practically annual epidemics in New Orleans. Not to get too Jared Diamond-y, but New Orleans was just more "tropical" and thus inclined to be developed in that way compared to more temperate areas that were familiar for European migration.
And this most certainly did influence the human factor of settlement and the types of work they were engaged in: Louisiana was much more "colonial" in this regard. The economy was agricultural and as such especially geared towards export cash crops grown on large plantations - obviously cotton but also notably sugar. By 1860, just under half of the population (46.9%) were slaves. Louisiana essentially had half its population barred from literacy and education until Reconstruction, and this is a big barrier to development in itself.
Even without those barriers, the Northeast was a ahead a bit in terms of literacy and education. Louisiana got its first college in 1825, almost a good two centuries after Boston (Harvard), and almost a century after New York (King's College/Columbia). Massachusetts and New York had higher literacy rates (Massachusetts in 1860 was close to universal), which came in part from older school laws and older public schools. New York and Boston therefore were in areas that had much more skilled workforces, and also more-developed capital markets (especially in New York) - thus they weren't just port cities exporting cash crops or resources, but already part of regions that were beginning to industrialize. Textiles were a big one in mill towns like Lawrence and Lowell, Massachusetts (the factories there used power looms that were water powered - Louisiana doesn't have the kinds of falls or rapids that the Northeast does and couldn't have really done this). But there were other major industries developing as well - armaments (the Springfield armory, but also Colt and Winchester), railroads (in the 1820s), whaling in New Bedford (whale oil being a major source of fuel before the Civil War), and the aforementioned financial sectors. And it wasn't just in New York and Boston, but in their surrounding regions and the Northeast in general, which was much more densely settled than the South, even Louisiana.
The upshot of this was that New Orleans was actually a big, wealthy city in 1860. It was the sixth biggest city in the US then, just behind Boston. But the wealth was incredibly concentrated into a mostly white planter class overseeing slave labor in a region that wasn't remotely as urbanized as the Northeast. New York was already the biggest city in the US, but Brooklyn (not part of NYC yet) was the third biggest city, and the second biggest city, Philadelphia was relatively close. New Orleans was the second biggest city in the South (after Baltimore), and really there were no other urban peers in the South at all - the next biggest cities were border cities of Louisville and Washington, DC, then Charleston, which was a fourth of New Orleans' size (40,000 people). Massachusetts had ten of the top fifty biggest cities in the US, many of these like Cambridge and Roxbury, just next to Boston. New York had eight of the top fifty, with three more just across the Hudson in New Jersey. It was already a very, very different scale in terms of economic activity.
