This is one case where MOST of the books have got the thing WRONG.
To Quote the usual Internet version of the information :
“The Piasa Bird is a Native American Cryptid depicted in one or 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 has been placed on a bluff in Alton, Illinois, several hundred yards upstream from its place of origin”.
John Russell account
The monster depicted in the mural was first referred to as the “Piasa Bird” in an article published circa 1836 by John Russell of Bluffdale, Illinois. John Russell was an imaginative professor of Greek and Latin at Shurtleff College, Upper Alton, Illinois. The article was entitled “The Tradition of The Piasa” and Russell claimed the origin of the word to be from a nearby stream : “This stream is the Piasa. Its name is Indian, and signifies, in the Illini, “The Bird That Devours Men” “. [note: The original “Piasa Creek” ran thru the main ravine in downtown Alton, and was completely covered by huge drainage pipes circa 1912.] According to the story published by Russell, the creature depicted by the painting was a huge bird that lived in the cliffs. Russell claimed that this creature attacked and devoured people in nearby Indian villages shortly after the corpses of a war gave it a taste for human flesh. The legend claims that a local Indian chief, named Chief Ouatoga, managed to slay the monster using a plan given to him in a dream from the Great Spirit. The Chief ordered his bravest warriors to hide near the entrance of the Piasa Bird’s cave, which Russell also claimed to have explored. Outoga then acted as bait to lure the creature out into the open. As the monster flew down toward the Indian Chief, his warriors slew it with a volley of poisoned arrows. Russell claimed that the mural was painted by the Indians as a commemoration of this heroic event.
Some sources report that this account was simply a story created by John Russell. In the book “Records of Ancient Races in the Mississippi Valley…” Chapter 2, 1887 by W. McAdams , the author says he contacted John Russell and Russell admitted the story was “somewhat illustrated” [He is also supposed to have told his son the story was “Made up”-DD]. The bird imagery is not reported in Father Marquette’s description, which makes no mention of wings. [emphasis added-DD] It is also possible that Marquette’s description and Russell’s account were both accurate for their respective times. The image may have been repainted at some point between 1673 and 1836 to revise its appearance and iconography.
When contemporary historians, folklorists, and tourism promoters are looking for a narrative description of the story behind the Piasa “Bird”, they often rely on Russell’s account. This colorful version of the tale can be adapted to allow a wide range of interpretation and allow other cities and counties to claim promotional rights to the legend.
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.
It seems that the original petroglyph was a different sort of creature entirely and that the image that had been originally reported,
by the 1840s sprouted wings, probably by way of some White Men restoring the image beyond what was actually warranted. About the time that Russell “Made up” his version of the story (together with the fanciful “Translation” of “The Bird that Eats Men”), the petroglyph looked like this:
And it seems that the creature had reversed position on the rock as part of the process. The 20th Century version now used is mostly fanciful but is ultimately a much-modified descendant of the 1840s version, with the wings becoming ever larger and sturdier
from Wikipedia, under “Discovery”:
In 1673, Father Jacques Marquette saw the painting on a limestone bluff overlooking the Mississippi River while exploring the area. He recorded the following description:
“While Skirting some rocks, which by Their height and length inspired awe, We saw upon one of them two painted monsters which at first made Us afraid, and upon Which the boldest savages dare not Long rest their eyes. They are as large As a calf; they have Horns on their heads Like those of a deer, a horrible look, red eyes, a beard Like a tiger’s, a face somewhat like a man’s, a body Covered with scales, and so Long A tail that it winds all around the Body, passing above the head and going back between the legs, ending in a Fish’s tail. Green, red, and black are the three Colors composing the Picture. Moreover, these 2 monsters are so well painted that we cannot believe that any savage is their author; for good painters in France would find it difficult to reach that place Conveniently to paint them. Here is approximately The shape of these monsters, As we have faithfully Copied It.”
Later French explorers, like St. Cosme, reported that by 1699 the series of images were badly worn due to the habits of the local Indians to “discharge their weapons” at the images as they passed. Author A.D. Jones, in his book ” Illinois and the West” c.1838, also describes the ravages of weapons (firearms) upon the images, and further refers to the paintings as being named “Piasua”.
Wikipedia illustration of The Underwater Panther or Misipizhiw from the article on the Piasa petroglyphs. The figure is important in many Native traditions and is frequently posted along waterways, also including the Great Lakes area. There is very little doubt that the original Piasa petroglyphs were variations on this design, which was also of importance to the Mississippian “Moundbuilder” cultures of the area.
While it actually is possible to locate Native words meaning “Bird” that sound like “Piasa” in the Eastern Woodlands area, it is pretty certain that the creature depicted was never thought of as a “Bird” at all. Furthermore, nearly everybody that quotes Russell’s story in more modern times wants to relate it to the Thunderbird legend and to modern sightings of what are also said to be Thundrebirds in the area. On the contrary, Thunderbirds are also known from Folklore of the area, in their usual “Bird” forms and not as flying “Piasa Birds”. They are depicted in traditional fashion to resemble larger eagles. And what is more, Folklore of the Great Plains insists that the Thunderbirds and the Underwater Panthers (or Horned Serpents) are at war with each other and are seeking each others’ extermination.
And the final blow seems to be that actually, “Piasa” seems to be taken as merely a variation on the term for Mishipizhiw, perhaps a generic trade term used throughout the Mississipian mound area. The website where this pipe was illustrated does so use the term “Piasa” as a composite creature of mostly-feline appearance and underworld associations, or in other words what is called Mishipizhiw (and with numerous variations) in other areas. The pipe is from Alabama. The source is the Smithsonian Institution, from the Collections of the National Museum of the American Indian.