One factor to a successful conclusion to any Vicksburg campaign was having officers of both services agree on the importance of controlling the Yazoo River. This meant that Yazoo had to be completely clear of enemy ground forces, ships, and torpedoes.
Around this time, U.S. Army cartographers produced two maps of the area that show why Porter, Sherman, and Grant placed such high value on the river. In order for Union ground forces to approach Vicksburg and be supplied from the north, the Yazoo River had to be under the U.S. Navy's complete control. (Note: Modern day maps of Vicksburg are extremely misleading, as the course of the Yazoo has been shifted to the south since the war ended.)
|December 1862 Map-The Yazoo River (on the left) and its relation to Vicksburg (lower right)|
|January 5 1863 Map of Vicksburg and the surrounding country side and rivers. The Yazoo River at the time|
emptied in to Mississippi west of Vicksburg and flowed from north to southwest.