This is an accurate depiction of the red quartzite almost hidden by prairie grass. Roberts Pass was intended to be included as part of the Prairie Grass Trail. Lead plant is often associated with little bluestem ("Schizachyrium scoparium"), a common prairie grass. A few Indians crept close to the American lines in the tall prairie grass. Site "B" is in similar condition, abandoned with prairie grass in a very remote location. Now, prairie grass covers less than 1% of Illinois. After a short fight, Opothleyahola's men set fire to the prairie grass and retreated. Switchgrass ("Panicum virgatum") is a native tallgrass prairie grass. Sod is prairie grass and dirt cut into blocks and stacked to form walls. Prairie grass has a much thicker, tougher root structure than a modern lawn. At that time, prairie grass covered the countryside at heights of 8 to 10 feet.