Wikipedia
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.
An Alton Evening Telegraph newspaper article of May 27, 1921 stated that seven smaller painted images, believed to be of archaic American Indian origin, were found in the early 20th century about 1.5 miles upriver from the ancient Piasa creature's location. These pictures were carved and painted in rocks located in the Levis Bluffs area by George Dickson and William Turk in 1905. Four of these paintings were of "an owl, a sun circle, a squirrel, and a piece showing two birds or some kind of animals in a contest", the other three paintings were of "a great animal, perhaps a lion, and another an animal about as large as a dog". These paintings were photographed by Prof. William McAdams and were to be placed in his book Records of Ancient Races in the Mississippi Valley: being an account of some of the pictographs, sculptured hieroglyphs, symbolic devices, emblems and traditions of the prehistoric races of America, with some suggestions as to their origin, William McAdams, C. R. Barns Publishing Co., 1887. {available on Google Books}. These seven archaic American Indian paintings have been lost in recorded annals as they were to have been in transit to the Missouri Historical Society c. 1922. Other Native American carved petroglyphs of a similar time period and region as the Piasa monster are carved into the rocks at Washington State Park, De Soto, Missouri (about 60 miles southwest of the current Piasa image) {location: N 38° 04.682 W 090° 41.033 15S E 703146 N 4217006}.
The 1797-1798 map of French explorer Nicolas De Finiels' shows the cliffs above the Piasa labeled as Hauteurs De Paillisa (source archives Versailles, France "Carte d'une Partie Du Cours Du Mississippi"). (Partial source: See Costa 2005: 297)
An earlier 1778 map titled "A new map of the western parts of Virginia, Pennsylvania, Maryland and North Carolina; comprehending the river Ohio, and all the rivers, which fall into it; part of the river Mississippi, the whole of the Illinois River, ... Author Hutchins, Thomas, 1730-1789" clearly shows the place name "PIASAS" where the present day City of Alton is located and bounded by the Wood River to the east. (this map is one of the earliest documented references for the word Piasa).
The name Piasa may also have been derived from the Native American Miami-Illinois word páyiihsa (cf. Anishinaabe: apa'iins(ag), "little people(s)"). This was their name for small, supernatural dwarves said to attack travelers. Local claims that the word Piasa meant "the bird that devours men" or "bird of the evil spirit" are not accurate nor based in the Illinois language.