Peg & I went to the Casa Grande National Monument about 20 minutes from the RV resort. It is an ancient four story building built from caliche mud and stacked up higher than I would have believed possible. The builders were stymied by a serious lack of suitable building materials; the floor support beams came from mountains better than 50 miles from the site covered by saguaro cactus sticks and topped with more caliche. The Casa Grande (big house) was built in the 1300s so it ended up being quite a bit more durable than I would have guessed. There is now a big steel shelter built over the top of it to keep it from turning into a gigantic pile of mud. The government experts at the site figured it has not less than 1300 tons of piled-up caliche which means they must have had quite a bit of labor and time to create the structure.
In the monument headquarters building they offer a video running in a little theater and the video explains how the indigenous folks lived around the big house. They lived in big walled compounds that had clan houses, some other public buildings and some flat-topped mounds that nobody is too sure about. There are also some structures believed to be ball courts and some remote family/clan dwellings outside the walls. About all that can be seen outside the Casa Grande main compound is foundation ruins.
Apparently, the experts believe the folks were around here for about 400 years but they abandoned ship not too long after the building was completed. It is believed or speculated that, despite extensive irrigation works around Casa Grande and a bunch of the Gila River Valley, there were initially some over-population issues but also a few years of heavy rain followed by many years of drought that made communal living impossible. The denizens broke up into small groups and dispersed to points elsewhere.