Casa Grande: The Tower With No Agreed Explanation

Four stories of caliche rise from the desert floor near Coolidge, Arizona, under a metal roof the federal government installed in nineteen thirty-two to keep the rain off a structure it could not explain. The roof is ugly. The building underneath it is extraordinary.

The Casa Grande Great House was built by the Hohokam around thirteen hundred and fifty CE, making it roughly six hundred and fifty years old. At four stories, it is among the largest known pre-Columbian structures north of Mexico, constructed from caliche, a calcium-carbonate soil that the Hohokam mixed with water and molded into walls up to four feet thick at the base. The building has stood for most of those six centuries without modern preservation. It stood through the Spanish colonial period, through the Mexican period, through Anglo settlement, and into an era when people came specifically to look at it.

The upper floor has circular holes cut into the walls that align with specific positions of the sun and moon at the spring equinox and at other astronomical events. This much archaeologists agree on. What the building was for remains disputed. Theories include an astronomical observatory for tracking planting calendars, a granary, a ceremonial center, and a residence for elite leadership. None of these interpretations is settled. The Tohono O'odham and Akimel O'odham maintain cultural connections to the site, and their oral traditions offer frames of understanding that the archaeological record cannot supply.

Casa Grande was among the first prehistoric structures in the United States to receive federal preservation attention, with an early protective roof installed in nineteen oh three. The current roof dates from nineteen thirty-two. The building that needed protection then has now outlasted several generations of the people who came to protect it.

It sits in the middle of the desert, still holding its purpose as its own private knowledge.