On this day in history - July 4th, 1863 - The Siege of Vicksburg ends with Vicksburg's surrender.
Major General Ulysses S. Grant spent the spring of 1863 trying to figure out how to capture the Confederate stronghold of Vicksburg. He launched several types of overland and amphibious campaigns against the city that failed; Grant then decided to cut loose of his supply train, cross the Mississippi south of Vicksburg and make for Jackson.
After capturing Jackson, Grant moved west toward Vicksburg, engaging Rebel forces at the Battle of Champion's Hill on the way.
Vicksburg was surrounded and invested for forty days. Of his siege, Grant wrote "My position is so strong that I feel myself abundantly able to leave it so and go out twenty or thirty miles with force enough to whip two such garrisons."
He accepted Lieutenant General John C. Pemberton's surrender on Independence Day. Tradition holds (falsely) that the city of Vicksburg did not celebrate on the 4th of July for many years.
After Vicksburg surrendered, the Federals controlled all of the Mississippi River, splitting the Confederacy in half and setting the stage for the closing stages of the Civil War.