Vicksburg is the fifth volume in a series of historical novels spanning the Civil War featuring the Brannon family of Culpeper County, Virginia. The focus turns to the west and the Southern stronghold of Vicksburg, Mississippi, where Cory Brannon is working to keep the town supplied by wagon train and railroad from Texas.

Vicksburg is the key to the Mississippi River and the future of the Confederacy, and Abraham Lincoln wants to put that key in his pocket. For almost a year the Federal army and navy have tried to dislodge the Confederates, but they have gained nothing. Finally, Union Gen. Ulysses S. Grant, the hero of the battles at Forts Henry and Donelson and the battle of Shiloh, is dispatched to take the town.

Cory and the woman he loves, Lucille Farrell, are working with her uncle, Col. Charles Thompson, and a small contingent of dedicated Southerners. In the spring of 1863, as the Union army begins to close in, Cory must abandon that venture to take on a vital mission for Confederate Gen. John Pemberton, the commander in charge of Vicksburg's defenses. At the end of Cory's journey, however, is an even more dangerous foray into Western Tennessee and over the border into Kentucky with the horse soldiers of Nathan Bedford Forrest, Cory's mentor from the battle of Shiloh. To help save Vicksburg, Cory becomes both a cavalry raider and even a spy.

Yet his efforts cannot prevent the inevitable as the Yankees eventually surround and lay siege to Vicksburg. With the Northern army set to seize the city, Lucille must also cope with additional challenges as she encounters a returning friend with secret plans of his own. The Federal bombardment, illness, injury, and starvation all take their toll on the defenders of Vicksburg, forcing Cory and Lucille to face decisions that threaten not only their love but their very lives.