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On July 4, 1863, General Ulysses S. Grant defeated the Confederate Army at Vicksburg, Mississippi, and the Union took control of this city. Why was this an important victory for the Union?
A.
The Union forced the Confederates out of the northern states.
B.
The Union took control of the Gulf of Mexico.
C.
The Union took control of the capital of the Confederacy.
D.
The Union then had control of all of the Mississippi River.