Visited Casa Grande, the oldest national archeologically park in the U.S. The people her practiced irrigated agriculture, using water from the Gila River. It was evidently a fairly prosperous community, with a population perhaps as much as 20,000, but was not sustainable. The civilization crashed around 1450 and the people dispersed. Local oral tradition blames war. More modern interpretation indicates climate change as a factor. The explanations are not mutually exclusive.
The Spanish discovered the ruins in 1694 and called it Casa Grande, or big house. Archaeologists are still studying the ruins. Some they leave buried in anticipation of better techniques in future.
The structures are not very big by modern standards, but consider that the buildings and irrigation systems were constructed using stone tools and sticks and w/o even the use of draft animals.