Hanging Rock is linked to a Miami legend in which Wy-nu-sa, unable to choose between two young braves who both loved her, called for a duel atop the rock so the winner would win her hand in marriage. On a moonlit night the two men climbed to the top and fought while she watched nearby. Though Wy-nu-sa secretly loved one more than the other, she never admitted it. When one brave fell over the edge to his death and the survivor came to claim her as his bride, she realized he was not the one she loved and, distraught, plunged to her own death. Hanging Rock rises 65 feet, was used by Native Americans as a lookout point, and has been recognized since the early 1900s as a rare geologic exposure, becoming a National Natural Landmark in 1986 and passing to ACRES Land Trust in 2008. The formation preserves three rock types from different parts of a Silurian seascape: a hard, massive dolomite cap rock, a middle section of well-bedded fossiliferous limestone and dolomite made of coral sand and larger reef fragments, and a soft dolomitic siltstone base deposited in quiet water before the reef formed. The Upper Wabash Valley contains notable ancient reefs in North America, and Hanging Rock is an erosional remnant of a reef formed about 420 million years ago when north-central Indiana lay about 15 degrees south of the equator beneath a shallow subtropical sea where corals, bryozoans, and other hard-shelled organisms built small pinnacle-like reefs just below sea level.