Answer: The victory gave the Union complete control of the Mississippi River.
Step-by-step explanation:
The statement that best describes the significance of the Union victory at Vicksburg to the outcome of the war is that the victory gave the Union complete control of the Mississippi River.
The strategic location on the Mississippi River helped in ensuring a win for the Confederate and the Union. The Siege of Vicksburg cemented the reputation of Grant and helped in ensuring victory of the Union.