On the horizon, the San Francisco Peaks rise as the highest mountains, forming the dominant feature of the san Francisco Volcanic Field. Imagine the sides continuing up to form one 16,000-foot-high mountain. This may be what the stratovolcano looked like about 500,000 years ago. The summit and flank of the volcano may have exploded and collapsed, much like Mount St. Helens. Erosion over thousands of years has created several peaks from the original volcano. Humphreys Peak, standing at 12,633 feet, is the tallest and is the highest peak in Arizona.
How did they get their name? The peaks were named in 1629 by a group of Franciscan missionaries in honor of St. Francis of Assisi. In 1847, a small West Coast settlement on the verge of becoming a boom-town changed its name from Yerba Buena to San Francisco. This happened more than 300 years after the Arizona peaks were christened.
Meghann M. Vance, Northern Arizona University Anthropology Laboratories