Casa Grande Ruins National Monument

Two days after Christmas we left Utah, traveling south for an 11-week trip. After a full day of driving we made our first stop at Casa Grande National Monument, a Hohokam archaeological site that centers around the 4-story great house (Casa Grande). I’ve been to numerous Ancestral Puebloan and Sinaguan dwelling sites but was really excited to visit my first Hohokam house; unlike many other prehistorical southwestern cultures the Hohokam built their above-ground structures of mud rather than stone. At Casa Grande, many of the hand-formed mud walls remain intact – both a testament to their superior construction and a boon to archaeologists and visitors alike.

The Hohokam were dwellers of the ancient Sonoran desert, an agricultural people who concentrated in the Salt and Gila River Valleys near modern Phoenix and along waterways and major drainages to the north and south. Despite living in the hot, extremely arid, and sometimes unforgiving lands in central and southern Arizona, the Hohokam developed agricultural technologies that allowed then to grow enough food to support tens of thousands of people and led to a flourishing of culture that produced remarkable pottery and shell jewelry. They also became important traders, poised between the Puebloans to the north and the multiple Mesoamerican groups to the south.

The Hohokam’s greatest agricultural accomplishments – and that for which they are primarily known for today – was their planning and creation of a massive, complex canal system to deliver water to fields and communities throughout the Phoenix Basin. Before modern dams were constructed upstream, both the Salt and Gila Rivers flowed year round, providing potential sources of water that would enable summer crops. At a few strategic points along both rivers, the Hohokam people placed mesquite weirs that diverted water into major canals, and from these trunk lines ran secondary canals to clusters of communities, and finally tertiary lines for directly irrigating fields. At each junction head gates controlled water flow, allowing agricultural production to be maximized in the event of drought. These canals were as long as 22 miles a piece, totaled about 600 miles, and irrigated single tracts as large as 70,000 acres; the Casa Grande canal system, for example, originated 16 miles away on the Salt River. It has been estimated that this irrigation system could produce enough food for 80,000 people – a number that is consistent with the number and placement of known settlements – making the Phoenix Basin the most densely populated area of the prehistoric Southwest. Both the recognition of the manpower needed to create and maintain these canals and the engineering knowledge behind the construction of drops of 1-2 feet per mile is incredibly impressive.

The peoples of the Hohokam culture underwent remarkable growth and evolution during their thousand year occupation of the basin, integrating new rituals from surrounding peoples, embracing and excelling in the construction of multiple forms of public architecture, and developing a centralized bureaucracy to manage food surplus. In summary, they were not only a highly developed prehistorical society but an extremely resilient and adaptable one, capable of both managing vast trade networks and incorporating elements of other cultures that suited them, and of both investing in the building of hundreds of ball courts and then abandoning them in favor of the construction of huge platform mounds and great houses. And of course, in addition to their creation of monumental architecture, pottery, and jewelry was their establishment and maintenance of canals.

By the mid-14th century the Casa Grande Site already contained multiple ball courts, large-scale plazas, and elevated platform mounds in addition to 7 large residential compound structures capable of housing up to 2,000 people. Examples of all these types structures can still be seen throughout the site today but the crowning jewel of the site was – and still is – the Great House, built in c. 1350 AD. Constructed of calcium rich hard pan mud called caliche and shaped by hand without the use of forms, the structure boasts a 4 foot walls at it’s base and a 4 story tower in the center. Small openings in the upper stories precisely align with astrological events. Surrounding the Great House are plazas, ringed by excavated room blocks of residential and storage compounds, and farther away are unexcavated ballcourts and platform mounds, the former of which appear as a large, shallow depression in the flat desert landscape.