Why Build the Casa Grande?

Suggested alignment holes in the walls of the Great House

NPS

Archeologists don't know for sure. Its original purpose remains a puzzle. Here, there are still more questions than answers.

Was it an ancient astronomical observatory? Perhaps. Why do the walls line up north-south-east-west? Unknown. We can still observe the sun and moon line up with certain holes in the wall before you, year in and year out. Were sacred ceremonies held here? Did a leader who oversaw the all-important irrigation canals work inside these rooms? Did an influential family or clan call the Casa Grande their home?

The answers remain unknown. The Casa Grande likely served many purposes, many functions. Why do you think the Ancestral Sonoran Desert People built this impressive multi-story building?

Farming societies in many parts of the ancient world worked out ways to track the seasons. The Casa Grande also has features that can be used to accurately mark the time of year.

Summer Solstice

Sunlight lines up through this small hole at sunset on the longest day of the year.

Spring and Fall Equinoxes

The rising sun lines up with twin openings in the top floor of the Casa Grande each March and September.

A Very Rare Lunar Event

The sun 'stands still' in the sky twice every year— at 'solstices.' The moon 'stands still' in the sky only once every 18.6 years. This hole marks that lunar event.

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PDF of the wayside (5,973 KB) is available.

 

• Purpose to the Great House

  
  

  Jacob Butler of the Salt River-Pima-Maricopa Indian Community shares a few stories about the Great House.

  Credit / Author:

  NPS, movie outtakes, thanks to volunteer editor Jenise Cook

  Date created:

  10/14/2020

  Audio Transcript

  [Jacob Butler] Well what we know about Casa Grande is that it in our oral traditions it’s known as a Vah Ki. And Vah Ki to me is a play on words cause one of those root words in there, Vah is water. And Ki in O-odham is house. So to me that’s a water house. A lot of these raised mounds and ball courts and these places like the Casa Grande ruins they’re all situated right next to water systems. ...water ways. And I think this one, the Gila River’s less than a mile away.

  The interesting thing about the Casa Grande ruins is a lot of the windows align with different times of the year. There’s a lot of people believe, and I kind a lean towards this too, is that they were using that area to mark certain times to plant, certain times to harvest. Significant times of the year will be found based on where the sun aligned with some of those windows. And so in that respect I think it’s similar to the Pueblo Grande ruins, which also had some of those same windows that align with some of the same times of the year.