Final answer:
Controlling the Mississippi River was a key element of the Union victory in the Civil War.
Step-by-step explanation:
A key element of the Union victory in the Civil War was splitting Confederate territory by controlling the Mississippi River. By gaining control of the Mississippi River, the Union was able to divide the Confederacy and cut off vital supply lines. This helped to weaken the Confederate forces and ultimately contributed to the Union's victory.
Learn more about Union victory in the Civil War