The Union established its single biggest must-have when it held on to Fortress Monroe, at the end of Old Point Comfort, Virginia. So long as the North held this position, it dominated shipping traffic in and out of Chesapeake Bay as well as the entrance to the James River. The second all-important spot for the Union was Cairo, Illinois, a sandy spit of land at the confluence of the Ohio and Mississippi Rivers. Colonel Ulysses S. Grant was there by the summer of 1861, holding on to a vital piece of real estate.

The trouble for the Confederacy was that, given the naval strength of the Union, it had so much more real estate to defend. There were thousands of miles of Atlantic and Gulf Coast shoreline where the Yankees could attack. But to Confederate planners, it was evident that New Orleans, because of its commercial wealth, and Richmond, because it was the national capital, were the most important places. There was also a long-shot chance that the Confederacy could go on the offensive in the Far West, and to that end, a major effort was made to enter the Arizona Territory.