Once more extracts with my commentary from those presentations as seen at the Civil War Museum, Kenosha, Wisconsin, USA.
"THE GIBRALTAR OF THE WEST"
"Rivers were a major means of transporting supplies from the upper Middle West to supply depots, where goods were moved by boat, train or wagon to armies operating in the field.One of the most important of such depots was located at Cairo, Illinois, at the convergence of the Ohio and Mississippi Rivers. B y 1855, the community already included levees, a dry dock and shipyard, sawmills, warehouses and an iron works.With the star of the war in April 1861, Cairo ('kay-row') became so strategically important that 2,300 soldiers with 15 pieces of field artillery were immediately sent to protect the site. Within months, it was a major military camp with thousand of soldiers, a parade ground, and several barracks. It also boasted a naval yard for outfitting wharfboats - flatboats with shed-like structures - with crews and ordnance. The Illinois Central Railroad carried soldiers, supplies and equipment to Cairo year-round, from The New York Times reported in detail on Cairo's military establishment, gun emplacements and chin of mines across the Mississippi River, calling it 'The Gibraltar of the West.'"
Cairo at the confluence of the Ohio and Mississippi rivers. A strategic location if there ever was one! Three states coming together at one point. Men and material as marshaled for the war effort gaining access further down river [the Mississippi] to those states in rebellion.