|Description: A map showing the canyon of the Snake River at the Seven Devils. Sketch contours, interval approximately 500 feet. The cross-lined areas represent basalt-covered surface; the blank areas represent older slates, schists, etc.|
Source: Isaiah Bowman, Ph. D., Forest Physiography (New York, NY: John Wiley and Sons, 1911) 195
Map Credit: The Private Collection of Roy Winkelman.