Long before modern calendars the prehistoric people of the American Southwest were tracking the movements of the sun with remarkable precision, and one of their most incredible creations can still be observed today at Petrified Forest National Park in Arizona.
Ancestral Puebloans constructed solar calendars throughout the Colorado Plateau, carving petroglyphs at specific angles to capture sunlight during solstices, equinoxes, and cross-quarter days. Likely similar in purpose to Stonehenge in the United Kingdom, the Cce, and Uxmal in Mexico’s Yucatan Peninsula, these markers represent a sophisticated understanding of seasonal cycles developed over several thousand years.
One of those markers sits at Puerco Pueblo, located 11 miles from the park’s north entrance and seventeen miles from the south entrance. A short paved trail leads visitors to a boulder featuring a small spiral petroglyph that functions as a precise summer solstice indicator. For roughly two weeks surrounding June 21st, a shaft of sunlight projects through a crack in the boulder and travels down its surface until it touches the center of the spiral. The effect peaks around 9am.
Park rangers will be on hand at Puerco Pueblo to guide visitors through the event. For those visiting outside of ranger hours, a wayside exhibit is located near the petroglyph along the side path from the main Puerco Pueblo trail.
Petrified Forest National Park is located in northeastern Arizona along Interstate 40. The summer solstice window closes quickly, so visitors hoping to witness the solar alignment should plan their trip soon.