SPRINGFIELD, Ill. (AP) — A sandstone canyon wall carved with Civil War graffiti is among 12 sites in Illinois that have been added to the National Register of Historic Places over the past year. The Thompson Brothers Rock Art site is located in Giant City State Park near Makanda in southern Illinois. The region served as a staging ground for Union forces. The names of three Union supporters are carved into the rock face. Among them are brothers Albert and Theodore Thompson. Albert served in two military units. Theodore was a marshal in charge of apprehending Union Army deserters in the area. It’s thought they carved their names as a warning to Southern sympathizers in a region with divided loyalties. Other sites added include the Jackson County Courthouse and Belleville’s Blair Historic District.