Rainbow Mountain is an ancient stratovolcano in northern California at the southern end of the Cascade Range, situated between Mount Shasta and Medicine Lake Volcano. Formed of andesitic and dacitic rocks during the Early Pleistocene, it belongs to a landscape shaped by some of the region’s best-known volcanic centers. Its last known eruption also occurred in the Pleistocene, marking it as a long-inactive volcanic feature rather than one associated with recent eruptions. It is recognized today as one of the Cascade volcanoes, part of the deep volcanic history of this area of California.