New Orleans, at the peak of its influence, was a very well-greased cog in an international, precipitously interdependent economy. This is not meant to drag on New Orleans, or even to disagree with the overall implied theme of the author's post -- I agree that geography in general (and rivers, in particular) is more significant than the common person gives it credit for, especially in pre-locomotive history. However, that conclusion was reached (through the example of New Orleans) in a rather dubious way, and it's important to understand why this example is questionable. As such, my first goal here is to argue that geopolitical influence, while concentrated within cities, is in fact distributed across the modern economy. While certain aspects of geopolitical significance are heavily-concentrated in specific regions (like agriculture in the Mississippi river basin), the "importance" of a region is directly correlated to the economic encouragement provided to that region by the greater, global economy. My second goal is to assert from a different, less economics-oriented angle, that rivers have played a rather important, if understated role in recent human history beyond the banal progression of running water->agriculture->larger population. In the approach I take, rivers served as an actual source of power, rather than a channel for goods that are necessarily tied to the global economy. But first, in the interest of addressing the flaws of New Orleans as an example for the importance of rivers...

New Orleans' peak influence was arguably on the eve of the American Civil War, when it had begun to challenge Liverpool for dominance in agriculture-based commerce. However, the argument is there to be made that, in fact, Liverpool was both the prime source and benefactor of New Orleans' wealth. In "Empire of Cotton: A Global Empire", Sven Beckert argues quite convincingly that the instruments allowing for the concentrated rate of capital generation, which were taken for granted as the southern economy boomed, were getting into place on stage-left, long before the Mississippi river basin became cotton fields. The socioeconomic infrastructures of efficient credit, capital and (predominantly slave-based) labor required to transform the Mississippi river basin into a cash-crop-based economy simply would never had existed without the joint influences of Liverpool to supply credit and Manchester to offer consistently rising demand. Everything, from the specific species of cash crops', to the slave labor used to harvest them, to the credit required to finance the purchases and transport thereof, revolved around the merchants of Liverpool. As the U.S. came to be the world's dominant producer of cotton (the antebellum figures are quite mind-boggling -- 77 percent of the 800 million pounds of cotton consumed in Britain, 90 percent of the 192 million pounds used in France, 60 percent of the 115 million pounds spun in the Zollverein, and 92 percent of the 102 million pounds manufactured in Russia), New Orleans certainly became a center for immense transfers of wealth and political clout -- alongside Charleston and Savannah, which enjoyed ports on the Atlantic, but lacked river-routes to the west.

However rich New Orleans was in resources and assets, its international significance was fundamentally tied to umbilical cord of foreign capital. During the ACW, the Confederacy faced huge financial obstacles in spite of possessing New Orleans -- largely because that essential conversion of crop-to-cash had begun to grind to a halt. So while New Orleans was a big player, it's quite a stretch to say she was the 'most geopolitically important city in world history'. Surely, the owner of that title wouldn't be so easily (tongue in cheek here, because it wasn't easy, as I describe shortly) brushed off by the global economy. Interestingly and tangentially, Beckert shows further how the ACW directly inspired global capitalists to hedge their sources of raw materials across many geopolitical regions, to prevent any single domestic war from causing international economic calamity in the future. Lack of access to New Orlean's resources devastated the European manufacturers who had grown dependent on American cotton, and the sting was sharp enough to attract investment elsewhere -- especially Egypt and India. In a way, New Orleans' antebellum supremacy guaranteed a strict upper bound on its future significance.

(continued below; sources at the end)