American Indian rock art is distributed across a portion of the east-flowing Arkansas River Valley in a distinctive spatial pattern in which motifs and compositions referencing spirit world subject matter predominate along the north side of the river, in contrast to imagery depicting the observable world on the south. This pattern accords with cosmological components of the belief systems of Dhegiha Siouan-speaking tribes, as expressed in the spatial elements of other cultural phenomena, including village layouts and ritual choreographies, among such groups as the Osage and Quapaw, who occupied the region during later historic times. One sandstone prominence also located south of the river attracted the attention of Precolumbian artists, who decorated its exposed surfaces with an intriguing depiction of a mask, partly obscured by lichen, exhibiting the telltale eyes and other characteristics of the Mesoamerican rain god Tlaloc. Examination of this image, along with a second possible Mesoamerican- or Southwestern-inspired image located north of the river, serves to enlarge our understanding of the wider distributional pattern, especially on the topic of how local communities incorporated exotic ideas into the fabric of their cosmological landscapes.