Port Hudson State Historic Site, in Lousiana, about an half hour north of present-day Baton Rouge, was the site of the longest military siege in American history. Control of the Mississippi River was an important goal for both sides of the Civil War. The North wanted the river to control supply movements and to split the Confederacy in two. The South wanted to maintain control and ensure the flow of supplies.
When New Orleans fell to the Union in April, 1862, the South's control of the Mississippi was in jeopardy. The Confederate army had already fortified the river bluffs at Vicksburg, Mississippi, but needed defenses below the mouth of the Red River, the primary route for shipment of supplies from Texas. The bluffs near the small town of Port Hudson were a good site for defensive positions - it was the first high ground upstream from Baton Rouge and overlooked a bend in the Mississippi. After defeat at the Battle at Baton Rouge, Aug 5, 1862, the South's army marched to Port Hudson, built a series of river batteries along the bluffs and a 4 1/2-mile line of earthworks to protect the land approach to the the river. A 48-day siege of Port Hudson began on May 23, 1863, with roughly 30,000 Union troops, under General Banks, against 6,800 Confederates, under General Gardner. On May 27, and again on June 14, the Union army launched assaults against the earthworks and trenches protecting Port Hudson, resulting in some of the bloodiest and most severe fighting of the War. As the siege continued, the Confederate army nearly exhausted their ammunition and they also had to do with eating mules, horses and rats. When word reached the Confederates that Vicksburg had surrendered, it was realized that their situation was hopeless and nothing could be gained by continuing the defense of Port Hudson. Surrender terms were negotiated, and on July 9, 1863, after 48 days and thousands of casualties, the Union took over Port Hudson.