An ancient four-story earthen structure stands at the northern edge of modern-day Coolidge — so impressive it was the first site to be designated an archeological reserve by the federal government, in 1892.
It’s sheltered by a steel roof erected 90 years ago, that in itself considered historic by modern society.
The building beneath it is believed to have been constructed around 1300, a marvel of human ingenuity and tenacity built without some of the innovations found in that era such as wheels or horses and other livestock.
Caliche from surrounding soils was poured in continuous layers to raise the walls of the compound, a technique accomplished today by sophisticated machinery.
The Great House or Casa Grande, as it was dubbed by Spanish explorer Father Eusebio Kino after he was led there by indigenous O’odham in the 17th century, was made possible by another such innovation, a network of canals diverting water from the river about a mile to the north.
These were dug throughout the Sonoran Desert along the Gila and Salt rivers by the ancestral Sonoran Desert tribes, known in archaeology as the Hohokam.
The grand edifice and the community that surrounded it was just west of an earlier canal-supported settlement known to archaeologists as the Grewe community, and next to a ball court which also preceded it.
It could have been built to oversee the canals that irrigated nearly 20,000 acres of agricultural land in the immediate area, to hold spiritual ceremonies, to trace celestial patterns through strategically placed windows, to house a chief and family or to serve multiple purposes.
Analysis of the pine logs and dried caliche used indicates it was designed and constructed at its full size. It must have served a critical purpose.
“What that importance was, that’s up for interpretation, the things that it was used for, but the one thing that comes out of it is that it was important. You don’t build a four-story structure, with all those labor hours, unless it has an extreme importance to you,” says Dave Carney, chief of interpretation and education at Casa Grande Ruins National Monument.
Archaeologists have documented a pattern of the rooms found within the Great House, with five each on the bottom two floors and a single room on the top level — the first floor was filled with dirt.
Burn marks indicated there were hearths in several of these rooms, hinting that people lived within them. Recovered artifacts point to processing corn, beans and other crops grown nearby. Intricate pottery and woven baskets point to an artisan culture, with some of these products traded to tribes near and far.
Evidence suggests the ancient culture that built this and similar structures along the Gila and Salt rivers ended around 1450 for reasons potentially related to climate, conflict or overpopulation. Survivors likely dispersed and, through their descendants, seeded cultures that live on in the Gila River Indian Community and other Arizona tribes.
The ancient canals provided a roadmap for many of those dug to serve white settlers’ farms around Coolidge under the San Carlos Irrigation Project, beginning in the 1920s.
Sources: www.archaeologysouthwest.org, www.nps.gov/cagr, www.loc.gov