Engineered to Last

Robert Ciaccio artwork, part of the wayside image

Commissioned art with restricted use

Picture the effort and skills needed to build something the size of the Casa Grande without modern power tools, wheels, beasts of burden, or support frames.

The Ancestral Sonoran Desert People used caliche, a desert soil rich in calcium carbonate, to raise the thick walls you see here. Caliche was dug and mixed with water in shallow pits to form a stiff concrete-like material. They shaped the mud by hand to form the walls up to the heights you see.

Look closely at these walls. Can you see horizontal lines? Those lines show "courses," the height a batch of caliche was piled in one work session before being left to dry. After a course dried out, the workers laid down a fresh batch of caliche mud on top. These builders' ingenuity and knowledge of local soils made it possible to construct a building that has lasted more than seven centuries.

Were there others like this?

Other Great Houses were found along the Gila River and in the Phoenix Basin. Archeologists believe another structure like the Casa Grande existed at the site of Pueblo Grande, an archeological park in Phoenix. Today, the Casa Grande remains the only example of a multi-story structure from the Hohokam culture.

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• Caliche Concrete

  
  

  David Winchester, park volunteer and retired park ranger, describes what caliche is and how to find it.

  Credit / Author:

  NPS, movie outtakes, thanks to volunteer editor Jenise Cook

  Date created:

  10/14/2020

  Audio Transcript

  My name is David Winchester. Retired Park Ranger, current volunteer. The structures at the monument, Casa Grande Ruins, are largely caliche structures. And by that I mean the local version of concrete. If you dig down anywhere here seems like a couple inches to a couple of feet, you’re going to run into this rock hard layer of soil. It’s a happy combination of the local clays and sands and a healthy dose of calcium carbonates. When you combine those it sets up very much like limestone. And this material is very useful once you learn how to use it. The ancestral Sonoran Desert people learned that if you use water you could actually soften this material up and it made it much easier to dig through in the process of digging a canal. And eventually somebody developed the idea: why don’t we use this material. After it’s been set aside it dries once again and resumes its very rock hard like form. And at some point somebody developed the idea of actually building walls with this material.