The Illinois State Memorial is located on Union Avenue at milepost 1.8, tour stop #2. Dedicated on October 26, 1906, the monument was transferred to the United States by Governor C.S. Deneen and accepted by J. S. Schofield of the United States War Department. It was erected by the firm of Culver Construction Company with William B. Mundie contracting the designers and sculptors. The design was by W. L. B. Jenney and sculptor was Charles J. Mulligan.
Stone Mountain (GA) granite forms the base and stairway. Above the base is Georgia white marble. There are forty-seven steps in the long stairway, one for each day of the Siege of Vicksburg. Modeled after the Roman Pantheon, the monument has sixty unique bronze tablets lining its interior walls, naming all 36,325 Illinois soldiers who participated in the Vicksburg Campaign. The monument stands sixty-two feet in height, and originally cost $194,423.92, paid by the state of Illinois.