The San Juan River, named by the Spanish San Juan Bautista (Saint John the Baptist), threads its way through Colorado, New Mexico, and Utah to the border of northern Arizona. With its headwaters in the San Juan Mountains of southwestern Colorado from which comes ninety percent of its flow, the river still drains nearly sixteen million acres of the Four Corners region as it drops from an altitude of 14,000 feet to approximately 3,600 feet above sea level. The flow of the river today is largely controlled by the waters released from Navajo Dam in New Mexico into the San Juan. The river's Utah portion is approximately 125 miles long; it then terminates as it flows into Lake Powell.
The river historically has played an important part as a continuous source of water in an arid climate. Anasazi ruins and rock-art panels dot its sandstone cliffs and floodplains. The San Juan also plays a significant role in Navajo mythology, where it is known as Old Age River, One-With-a-Long-Body, or One-With-a-Wide-Body, and is characterized variously as an old man with hair of white foam, a snake coiled at the Goosenecks, a flash of lightning, and a black club of protection. This latter theme is important to the Navajos, who, even before the river became an official reservation boundary in 1884, viewed it as a line of separation between their safe confines and the land of the Utes and white men.