The South had only one through line from the Atlantic to the Mississippi; and this ran across that Northern salient which threatened the South from the southwestern Alleghanies. The other rails all had the strategic defect of not being convenient for rapid concentration by land; for most of the Southern rails were laid with a view to getting surplus cotton and tobacco overseas.
The strategic gap at Petersburg was due to a very different cause; for there, in order to keep its local transfers, the town refused to let the most important Virginian lines connect.
Taking sea-power in its fullest sense, to include all naval and mercantile parts on both salt and fresh water, we can quite understand how it helped the nautical North to get the strangle-hold on the landsman's South. The great bulk of the whole external trade of the South was done by shipping. But, though the South was strong in exportable goods, it was very weak in ships. It owned comparatively few of the vessels that carried its rice, cotton, and tobacco crops to market and brought back made goods in return. Yankees, Britishers, and Bluenoses (as Nova Scotian craft were called) did most of the oversea transportation.
Moreover, the North was vastly stronger than the South on all the inland waters that were not "Secesh" from end to end. The map shows how Northern sea-power could not only divide the South in two but almost enisle the eastern part as well. Holding the Mississippi would effect the division, while holding the Ohio would make the eastern part a peninsula, with the upper end of the isthmus safe in Northern hands between Pittsburgh, the great coal and iron inland port, and Philadelphia, the great seaport, less than three hundred miles away. The same isthmus narrows to less than two hundred miles between Pittsburgh and Harrisburg (on the Susquehanna River); and its whole line is almost equally safe in Northern hands. A little farther south, along the disputed borderlands, it narrows to less than one hundred miles, . from Pittsburgh to Cumberland (on the Potomac canal). Even this is not the narrowest part of the isthmus, which is less than seventy miles across from Cumberland to Brownsville (on the Monongahela)and less than fifty from Cumberland to the Ohiopyle Falls (on the Youghiogheny). These last distances are measured between places that are only fit for minor navigation. But even small craft had an enormous advantage over road and rail together when bulky stores were moved. So Northern sea-power could make its controlling influence felt in one continuous line all round the eastern South, except for fifty miles where small craft were concerned and for two hundred miles in the case of larger vessels. These two hundred miles of land were those between the Ohio River port of Wheeling and the Navy Yard at Washington.
Nor was this virtual enislement the only advantage to be won. For while the strong right arm of Union sea-power, facing northward from the Gulf, could hold the coast, and its sinewy left could hold the Mississippi, the supple left fingers could feel their way along the tributary streams until the clutching hand had got its grip on the whole of the Ohio, Cumberland, Tennessee, Missouri, Arkansas, and Red rivers. This meant that the North would not only enjoy the vast advantages of transport by water over transport by land but that it would cause the best lines of invasion to be opened up as well.
Of course the South had some sea-power of her own. Nine-tenths of the United States Navy stood by the Union. But, with the remaining tenth and some foreign help, the South managed to contrive the makeshift parts of what might have become a navy if the North had only let it grow. The North, however, did not let it grow.
The regular navy of the United States, though very small to start with, was always strong enough to keep the command of the sea and to prevent the makeshift Southern parts of a navy from ever becoming a whole. Privateers took out letters of marque to prey on Northern shipping. But privateering soon withered off, because prizes could not be run through the blockade in sufficient numbers to make it pay; and no prize would be recognized except in a Southern port. Raiders did better and for a much longer time. The Shenandoah was burning Northern whalers in Bering Sea at the end of the war. The Sumter and the Florida cut a wide swath under instructions which "left much to discretion and more to the torch." The famous Alabama only succumbed to the U.S.S.
Kearsarge after sinking the Hatteras man-of-war and raiding seventy other vessels. Yet still the South, in spite of her ironclads, raiders, and rams, in spite of her river craft, of the home ships or foreigners that ran the blockade, and of all her other efforts, was a landsman's country that could make no real headway against the native seapower of the North.