high as 250 feet, extending some 100 miles north and south of the city. Its western boundary was the river itself. To the east, it was a focal point of a rich cotton producing area, drawing commerce from the midwestern part of Mississippi. On the northeastern side of the city was the Yazoo River and its delta, a stretch of swampy bottom land stretching 175 miles from north to south, 60 miles from east to west. The ground just south of Vicksburg was almost as swampy and impassable. The Confederates had fortified the river bluffs from Haynes Bluff on the Yazoo down to the Grand Gulf at the mouth of the Big Black River, some 40 miles below (map at end of text). Across the river and to the west were the flatlands of Louisiana, a natural barrier to military movement. This area was equally swampy, interlaced by the course of the Mississippi River itself. Vicksburg stood atop it all.
The city could not be assaulted from the river, and sailing past it was risky and useless for attackers. The river formed a half-circle at this point, and the mortars on the high bluffs threatened any vessel that tried to slip by. For the Union troops to have any success, they would have to get to the high, dry ground east of the city. This would put them between two strong enemy forces. General John Pemberton, CSA, commanded 30,000 men in Vicksburg, while the supreme commander, General Albert Johnston, CSA, concentrated his troops at Jackson, Mississippi, located only 40 miles east of Vicksburg. The Union forces could easily have been caught in a vice.
In March 1863, Grant and Porter drew up a plan. Grant decided to use part of his forces above Vicksburg to cause a distraction, while the main body marched southward on the west side of the river, crossed over the east bank, and struck out inland. Porter's gunboats and other vessels, which up to now were on the river north of Vicksburg, were to slip past the Confederate bluff mortars dur...