On this day in 1863, a day after the Union win at Gettysburg,

CONFEDERATES SURRENDER VICKSBURG

 TO U.S. GRANT

On this day in 1863, the Confederates surrendered Vicksburg after a long siege by Union General Ulysses S. Grant.  The Union's victory at Vicksburg was the biggest of the western campaign and allowed the Union to control the Mississippi, effectively split the Confederacy, and disrupt the Confederacy’s supply lines.  Combined with the Union’s victory at Gettysburg the day before, the fall of Vicksburg rendered a double body blow of the first order to the Confederate cause.  Legend has it that the people of Vicksburg did not celebrate July 4th again until 1944 during WWII.

Wikipedia: The Siege of Vicksburg

Wikipedia: The Vicksburg Campaign