The Thompson Brothers Rock Art is an inscribed rock located within Giant City State Park in Union County, Illinois. Four names are carved into the rock, all but possibly one of which were inscribed by Union soldiers or supporters during the Civil War. The two most prominent signatures belong to brothers Albert S. and T. W. Thompson; the former was a Union soldier, while the latter served as Deputy Provost Marshal and was responsible for locating Union deserters. Union soldier Thomas L. Bailey also carved his name into the rock; the fourth name, A. Parker, may have been either a fellow soldier or a resident of the area who added his name after the war. The rock was carved at a time when Union supporters and Southern sympathizers fought for control of southern Illinois, and as the Thompson f