Answer:
1). Control over Vicksburg was important because of the Mississippi river which promotes trade and communication between Confederate states. The Union navy resorted in seizing a ship carrying Confederate diplomats going to Great Britain and France.
2). It was arguable said that they stood the test of time too long because of social unity within amongst the Southern society.
Not withstanding their race, class, gender, and regional antagonisms and also similarly, all historians recognize the enormous force brought to bear by Northern armies and the high casualties suffered by Confederate soldiers.