The Piasa or Piasa Bird is a Native American dragon depicted in one of two murals painted by Native Americans on bluffs (cliffsides) above the Mississippi River. Its original location was at the end of a chain of limestone bluffs in Madison County, Illinois at present-day Alton, Illinois. The original Piasa illustration no longer exists; a newer 20th-century version, based partly on 19th-century sketches and lithographs, has been placed on a bluff in Alton, Illinois, several hundred yards upstream from its origin. The location of the present-day mural is at 38.898055, -90.19915. The limestone rock quality on the new site is unsuited for holding an image, and the painting must be regularly restored. The original site of the painting was a high-quality (6–8 foot thick) layer of lithographic limestone, which was predominantly quarried away in the late 1870s by the Mississippi Lime Company. The ancient mural was created prior to the arrival of any European explorers in the region, and possibly before 1200 CE. The location of the image was at a river-bluff terminus of the American Bottoms floodplain. It may have been an older iconograph from the large Mississippian culture city of Cahokia, which began developing about 900 CE. Cahokia was at its peak about 1200 CE, with 20,000 to 30,000 residents. It was the largest prehistoric city north of Mexico and a major chiefdom. Icons and animal pictographs, such as falcons, thunder-birds, bird men, and monstrous snakes were common motifs of the Cahokia culture. The Piasa creature may have been painted as a graphic symbol to warn strangers traveling down the Mississippi River that they were entering Cahokian territory.