The Siege of Vicksburg, which lasted from May 18 to July 4, 1863, was significant because it gave the Union control of the Mississippi River.

This victory was crucial in splitting the Confederacy in two and disrupting their supply lines. The Union, led by General Ulysses S. Grant, successfully besieged the city, resulting in the surrender of Confederate forces under General John C. Pemberton. The loss at Vicksburg, coupled with the Union victory at Gettysburg shortly after, marked a turning point in the Civil War, shifting momentum firmly in favor of the Union.