Saw this little text on the map about the mississippi control (just under 10sw if union controls the river).
There is nothing in the rulebook about this, so what does it mean?
Not sure which edition you have....but in the 2000 edition, there is a blue box that says "Union Control of Mississippi +10 SW - 1 CSA Rein"
So we go to the rule book:
12.8 The Mississippi River wrote:
If the Union player during the Political Control Phase has naval control of all spaces on the Mississippi River, he gains 10 SW points (i.e., if the Confederate player does not have any fort or ironclad [not Hunley] in any of the river port spaces). This is a one-time bonus and is not lost if the Confederate later recaptures one or more spaces on the river.
Dave Rubin already noted what happens with the -1 CSA Rein, so I'll let that go. :-)
Hope this helped!