Here is a short excerpt from my files.
The Crow Creek site mentioned dates to the early 1300's, certainly prior to European contact.
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However, most of these victims came from Crow Creek Canyon, the site of a large-scale massacre involving a minimum of 486 individuals (Gregg et al 1981). The excavators report that not only were almost every person scalped, but they also were mutilated and dismembered, and many of their hands and feet appear to have been removed and taken as trophies. This custom has been documented historically for certain Native American culture groups in the United States (Friederici 1907). Thus, it appears that something quite different from small scale raiding activities was occurring at Crow Creek Canyon. Furthermore, the skeletal remains were so mixed as to preclude the possibility of assigning post-cranial elements with the proper skulls, so detailed information about individuals is not available. Crow Creek is included in the study only because it gives evidence of the intensity of conflict in the Northern Plains during the mid-fourteenth century, and because two of the crania found at the site demonstrated a lesion of the frontal and parietals consistent with survival of a scalping incident. Presumably those two earlier scalping events were unrelated to the massacre itself, and therefore can be included in the analysis of scalping survivors discussed below....
.... It could be argued, then, that scalping in pre-Columbian America was more likely the result of raiding activity than of large-scale warfare taking place on a battlefield. The evidence for such an assertion is that women were not generally known to be warriors during historic times, and therefore, would be more likely to be scalped in or near their own villages (although see Ewers 1994).