The petroglyphs and pictographs of the American Southwest are intriguing, but we commonly ask what they "mean". Religion on the Rocks redirects our attention to the equally important matter of what compelled ancient peoples to craft rock art in the first place. To examine this question, Aaron Wright presents a case study from Arizona's South Mountains, an area once flanked by several densely populated Hohokam villages. Synthesizing results from recent archaeological surveys, he explores how the mountains' petroglyphs were woven into the broader cultural landscape and argues that they are relics of a bygone ritual system in which people vied for prestige and power by controlling religious knowledge. The features and strategic placement of the rock art suggest this dimension of Hohokam ritual was participatory and prominent in village life. Around AD 1100, however, petroglyph creation and other ritual practices began to wane, denoting a broad transformation of the Hohokam social world. Wright's examination of the South Mountains petroglyphs offers a narrative of how Hohokam villagers negotiated a concentration of politico-religious authority around platform mounds. Readers will come away with a better understanding of the Hohokam legacy and a greater appreciation for rock art's value to anthropology.