This study investigates the role that Engineer Operations played in the Vicksburg Campaign of the American Civil War. A background study and description is made of the structure, composition, capability, and employment of engineer officers and units during the American Civil War. The Vicksburg Campaign is analyzed in detail to determine the contributions that Engineer Operations made to the Campaign's success. The Campaign is broken down into four phases: (1) the Confederate Fortification of Vicksburg, (2) operations in the Bayous, (3) the Campaign of Maneuver, and (4) the Siege of Vicksburg. Each phase is examined in an engineer context to determine what type of Engineer Operations were conducted and whether they were critical to that phase and the Campaign overall. The final conclusions derived from this study are that Engineer Operations were critical to the successful outcome of the Campaign.