Myths and Legends of our Own Land, by Charles M. Skinner, , at sacred-texts.com
Not far west of St. Louis the Lake of Creve Coeur dimples in the breezes that bend into its basin of hills, and there, in summer, swains and maidens go to confirm their vows, for the lake has an influence to strengthen love and reunite contentious pairs. One reason ascribed for the presence of this spell concerns a turbulent Peoria, ambitious of leadership and hungry for conquest, who fell upon the Chawanons at this place, albeit he was affianced to the daughter of their chief. The girl herself, enraged at the treachery of the youngster, put herself at the head of her band—a dusky Joan of Arc,—and the fight waged so furiously that the combatants, what were left of them, were glad when night fell that they might crawl away to rest their exhausted bodies and nurse their wounds. Neither tribe daring to invite a battle after that, hostilities were stopped, but some time later the young captain met the girl of his heart on the shore, and before the amazon could prepare for either fight or flight he had caught her in his arms. They renewed their oaths of fidelity, and at the wedding the chief proclaimed eternal peace and blessed the waters they had met beside, the blessing being potent to this day.
Another reason for the enchantments that are worked here may be that the lake is occupied by a demon-fish or serpent that crawls, slimy and dripping, through the underbrush, whenever it sees two lovers together, and listens to their words. If the man prove faithless he would best beware of returning to this place, for the demon is lurking there to destroy him. This monster imprisons the soul of an Ozark princess who flung herself into the lake when she learned that the son of the Spanish governor, who had vowed his love to her, had married a woman of his own rank and race in New Orleans. So they call the lake Creve Coeur, or Broken Heart. On the day after the suicide the Ozark chief gathered his men about him and paddled to the middle of the water, where he solemnly cursed his daughter in her death, and asked the Great Spirit to confine her there as a punishment for giving her heart to the treacherous white man, the enemy of his people. The Great Spirit gave her the form in which she is occasionally seen, to warn and punish faithless lovers.