Given its importance, it's somewhat surprising in retrospect that the Union managed to capture New Orleans in an easier manner than places like Vicksburg and Atlanta. Admiral David Farragut's naval forces battered their shaky Confederate counterparts and were able to get over a dozen ships upriver past a couple of crucial Confederate forts along the Mississippi. By May 1862, Union forces occupied the city and General Benjamin Butler became its military governor, leaving the last true bastion of Confederate defenses on the Mississippi at Vicksburg.

At the start of 1863, Robert E. Lee's Army of Northern Virginia had been frustrating the Union in the Eastern theater for several months, but the situation in the West was completely different. The Confederates had lost control of several important states throughout 1862, and after New Orleans was taken by the Union, the North controlled almost all of the Mississippi River, which Confederate general James Longstreet called "the lungs of the Confederacy". By taking control of that vital river, the North would virtually cut the Confederacy in two, putting the South in a dire situation.

The only domino left to fall was the stronghold of Vicksburg, and both sides knew it. The Union Army of the Tennessee, led by Ulysses S. Grant, would spend months trying to encircle the army and eventually force John Pemberton's Confederate army to surrender. Grant eventually succeeded on July 4, 1863, but since it came a day after the climactic finish of the Battle of Gettysburg, Vicksburg was (and still is) frequently overlooked as one of the turning points of the Civil War. In fact, had the Confederate's military leadership listened to Longstreet, who advocated detaching soldiers from Lee's army to head west and help the Confederates deal with Grant or Rosecrans in that theater, the Battle of Gettysburg might never have happened.