The Illinois Memorial, honoring Union army soldiers from Illinois who fought at the Siege of Vicksburg, was dedicated at Vicksburg National Military Park.

The Illinois Memorial is a public memorial located at Vicksburg National Military Park in Vicksburg, Mississippi, United States. Dedicated in 1906, it honors the Union Army soldiers from Illinois who fought in the siege of Vicksburg during the Vicksburg campaign of the American Civil War. It was designed by architect William Le Baron Jenney and sculptor Charles Mulligan. It is known to the locals as Echo Hall or the Hollar House.

During the American Civil War, the United States Army, the land force that fought to preserve the collective Union of the states, was often referred to as the Union army, the federal army, or the northern army. It proved essential to the restoration and preservation of the United States as a working, viable republic.

Illinois is a state in the Midwestern region of the United States. It borders Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash and Ohio rivers to its south. Of the fifty U.S. states, Illinois has the fifth-largest gross domestic product (GDP), the sixth-largest population, and the 25th-most land area. Its capital city is Springfield in the center of the state, and the state's largest city is Chicago in the northeast.

The siege of Vicksburg was the final major military action in the Vicksburg campaign of the American Civil War. In a series of maneuvers, Union Major General Ulysses S. Grant and his Army of the Tennessee crossed the Mississippi River and drove the Confederate Army of Mississippi, led by Lieutenant General John C. Pemberton, into the defensive lines surrounding the fortress city of Vicksburg, Mississippi, leading to the successful siege and Confederate surrender.