One of Grant's most important victories was at Vicksburg, which ___________.

was the South's most important port city on the Gulf Coast
caused Lee to surrender
destroyed the South's important sugar cane crops gave the Union control of the Mississippi River

gave the Union control of the Mississippi River

Is that correct

Yes, that is correct. Grant's victory at Vicksburg gave the Union control of the Mississippi River, which was a crucial strategic advantage during the Civil War.