 The designs are divided into four distinct groups; three of these are on the center and ends of the rock shelter's wall, while the fourth is on a joint block of sandstone within the shelter.Most of the designs were created during the Late Woodland and Mississippian periods, which spanned from 450 to 1550 A.D.; a number of the figures were added after 1550.A tall spear-holding anthropomorph in the western group is the largest individual petroglyph in Illinois.