Find mysterious rock art and quiet beauty at ancient sites near Phoenix

Phoenix, the Southwest’s favorite poster child for the plague of urban sprawl, has been sprawling for a lot longer than most people imagine―about 800 years.

The Salt River Valley cradling metropolitan Phoenix was the largest population center in the prehistoric Southwest; archaeologists estimate that between 20,000 and 50,000 people lived there during the 12th and 13th centuries. The native Hohokam built 1,000 miles of irrigation canals. Some of their villages, the houses crafted of puddled adobe, were strewn along these ditches for more than half a mile. “If you compare them with contemporary Europe,” says Phoenix city archaeologist Todd Bostwick, “these were major cities.”

The attraction for the Hohokam was a desert river that flowed year-round and a warm climate that spread harvests and the gathering of wild food throughout the year. When the civilization dissolved, the Hohokam left behind a lot to ponder ― architecture, rock art, pottery, jewelry, and the enormous, enigmatic platform mounds that the Hohokam built and expanded during their final 300 years in the Sonoran Desert.

Petroglyph mysteries

Prehistoric petroglyphs pepper the hills and mountains ringing the city, although why the Hohokam chose to cluster them around certain sites is debatable. And scholars are still pursuing their meaning.

“One of our goals is to have people get comfortable with not having answers,” says Peter Welsh, director of the Deer Valley Rock Art Center in northwest Phoenix. “The one thing we’re fairly sure of is that it’s not trivial―people make rock art with serious intent.” Welsh ticks off the theories: the glyphs may be records of clan migrations, initiations, territory markers, or efforts to summon supernatural help. Whatever the petroglyphs represent, Deer Valley has the best collection near Phoenix: more than 1,500 glyphs were pecked into the basalt boulders.

The most astounding remnant of Hohokam architecture is the “Big House” at Casa Grande Ruins National Monument, 50 miles south of Phoenix. No one knows why the Hohokam built three- and four-story structures, although Casa Grande, the only one still standing, has openings in its walls that align with solstices and equinoxes. Solar calendars would have helped farmers stage their plantings and harvests, but the calendars wouldn’t have needed to be in high-rises―unless this knowledge was protected as a shamanic secret.

In the desert northeast of Phoenix, the little-known Sears-Kay Ruin crowns a tall hill, raising the question that surrounds so many late pre-Columbian villages in the Southwest: did the Hohokam build for defense? A wall of boulders enclosed the 40-room compound, suggesting a defensive posture―but it would have been a long walk to the wash below for water, exposing the water carriers to ambush. 

The battle over warfare

The current dispute in Southwestern archaeology is about prehistoric warfare. Harvard University archaeologist Steven A. LeBlanc believes that the cultures of the Southwest were engulfed in struggles over territory and natural resources for centuries, especially after 1200. He feels that natives had no choice; survival was on the line. “Just because we live in an era of senseless wars does not mean war was always senseless,” LeBlanc writes in his 1999 book, Prehistoric Warfare in the American Southwest.

But Bostwick says physical evidence for Hohokam warfare is pretty thin; most skeletal evidence doesn’t suggest violent deaths. “In 100 burials, there will be maybe one or two with an arrowhead or a skull cracked with an ax,” he explains. “That’s just the normal level of violence associated with any society.”

Still, some profoundly serious social reorganization occurred in the Hohokam heartland around 1200. This theory could help explain why there’s a football field-size platform mound rising up to 15 feet high outside Bostwick’s office at Pueblo Grande Museum.

Beginning around 1150, the Hohokam elevated structures in their villages by heaping dirt into enormous, honeycomb-like series of rectangular cells. They surrounded these platform mounds with walls of caliche, granite, and adobe mortar―apparently to restrict access―and then built adobe compounds on top.

Like other Southwestern cultures, Hohokam civilization collapsed long before Europeans arrived. The Akimel O’Odham and Tohono O’Odham, likely Hohokam descendants, were living a much simpler and less urbanized life by the time Spaniards reached today’s Arizona in the 1500s. Archaeologists argue about the cause of the Hohokam society’s collapse, imagining soil salinization, droughts, floods, warfare, and epidemics.

But the most likely reason is the simplest: the population outstripped the natural resources of the land. Imagine what 50,000 people harvesting firewood would do to the Salt River Valley’s slow-growing stock of mesquite or to its small game animals. Archaeologists know from skeletal studies that the Hohokam suffered from malnutrition; their high-carbohydrate diet left them protein-starved.

Even in prehistoric times, the desert did not suffer urban sprawl gladly. 

Tracing the Hohokam

For general Phoenix-area travel and lodging information, contact the Greater Phoenix Convention & Visitors Bureau ( or 877/225-5749).

Casa Grande Ruins National Monument. The only remaining Hohokam “Big House” that’s still standing. 8-5 daily; $3. East of Coolidge at intersection of State 87 and State 287; or (520) 723-3172.

Deer Valley Rock Art Center. More than 1,500 petroglyphs; visit early when sun-light faces the rock art. Through Apr, 9-5 Tue-Sat, 12-5 Sun; May-Sep, 8-2 Tue-Fri, 7-5 Sat, 12-5 Sun; $5. 3711 W. Deer Valley Rd.; or (623) 582-8007.

Heard Museum. World-class permanent exhibits on prehistoric cultures of the Southwest, plus changing shows of historic and contemporary Native American art. 9:30-5 daily; $7. 2301 N. Central Ave.; or (602) 252-8848.

Pueblo Grande Museum and Archaeological Park. Excavated ruins, plus museum exhibits on Hohokam life. 9-4:45 Mon-Sat, 1-4:45 Sun; $2 (free on Sun). 4619 E. Washington St.; or (602) 495-0901.

Sears-Kay Ruin. Boulders encircle this mysterious 40-room hilltop compound. Open dawn to dusk daily for nonguided visits; free. Cave Creek Rd., 9 miles east from its intersection with Tom Darlington Rd. in Carefree; (480) 595-3300.

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