"Strategy is a system of expedients."
Von Molke
On an 8 1/2 X 11" map of the Western Theater of the Civil War, the entire operations of the Armies of Northern Virginia & of the Potomac is literally the size of a postage stamp. As events showed, the rest of the Confederacy could exist quite nicely without Virginia. The opposite was obviously not true. When isolated from supplies from the Western states, Lee's army dwindled & starved.
The topic of the thread is strategic sites. I don't propose to rate them, by definition a strategic asset is important.
Saltville, Smyth County Virginia produced 2/3rds of the salt consumed by the Confederate States. On the Gulf Coast, most of the blockade runners captured had cargos of salt. Not only is salt necessary for life, but during the 1860's, copious supplies of salt were needed to conserve meat. The saltworks at Saltville were a strategic asset that was attacked repeatedly. It speaks volumes that even as late as October 1864 the defenders far outnumbered attackers & successfully repulsed all assaults. Stoneman's Raid December 1865 defeated the defenders & completely destroyed the single greatest source of salt in the Confederacy. Real suffering followed.
The only source of copper in the Confederacy was Copper Hill near Chattanooga. The only copper mill was at nearby Cleveland, Tennessee. One of Grant's frist orders after taking command at Chattanooga was to order the destruction of the copper mill at Cleveland. From that point on, the Confederacy was entirely dependent on imports for its supply of caps. Copper Hill / Cleveland copper mill were strategic assets that Grant wasted no time in controlling.
There were nine black powder mills in the Confederacy. When A. S. Johnston abandoned both Nashville & the powder mill at the site of present day Old Stone Fort State Park near Manchester TN, a substantial part of the powder production was lost. The mill at the Armory in Augusta, Georgia produced powder of excellent quality. By 1864, it was the major source for ammunition for what was left of the Confederacy. For reasons not well understood, the strategic importance of Augusta was never recognized. Had it been, there is no doubt that no stone would have stood upon another when Sherman marched to the sea.
The agricultural production of North Georgia was a strategic asset of inestimable value. Before Sherman initiated his March to the Sea a ground breaking map was produced. It married data from the 1860 Census with a map of the State of Georgia.
Detail of Sherman's map of Georgia with county by county census data. LOC
Using this map, Sherman was able to direct his route to where it could do the most harm to the Confederate war economy.
The legend makes clear the detailed intelligence that was included in the map.
These counties have all strategic assets & agricultural production clearly depicted.
Sheman's personal map of North Georgia. LOC
The fold lines on this map are actually mark separate pieces of card that were pasted on linen.
Sherman carried this map in the map pocket in the tail of his coat.
A strategic goal of the March to the Sea was intended to break the morale of the Confederate public. A second strategic goal was to destroy the agricultural & manufacturing production of Northern Georgia that was an absolutely vital source of supplies for Lee in Virginia & other Confederate armies still in the field. Because he had these ground breaking maps, Sherman was able to target individual strategic assets such as mills & manufacturing facilities. He was able to both destroy agricultural production & feed his army using the census agricultural output data. Sherman stated that he would never have attempted the March to the Sea without these maps.
The strategic target that was the slave market of New Orleans was the largest in the U.S. Commodity production using slave labor had stopped being a paying proposition in Virginia & border states as early as the late 1850's had ceased to be a paying proposition. It was the sale of "extras", the market term for surplus labor sold away from Virginia & the border states. In the 1840's Franklin & Armfield had created the template for making fortunes transporting extras to the Forks in the Road slave market in Natchez, Mississippi. The Virginia aristocracy were dependent on raising human beings for sale for their economic survival. The majority of that trade passed through New Orleans. The banks & other financial functions that the Deep South depended on were, inevitably, in New Orleans as well. By taking New Orleans, the Union halted the flow of "extras" that were the source of slaves to replace the steady attrition of prime labor as the seven year useful lifespan of slaves ended, real labor shortages began to restrict production in the Deep South strangled production. Cut off from a large percentage of their cashflow, Virginia planters suffered accordingly.
When Grant secured Knoxville & Chattanooga, the strategic direct tail route between Virginia & Georgia was denied the Confederacy. By way of example, after the withdrawal from Knoxville, Longstreet's supplies during the winter were forced to take a convoluted round about route from Dalton, Georgia that often failed completely. The additional wear & tear of the 1,000 mile round trip was something the creaky Southern rail system could not sustain.
These are examples of the numerous strategic assets in the West that the Confederacy could not exist without. There are many others, but this variety of strategic points gives a clear indication of just where the strategic crown jewels lay.