One of the most distinctive things about Chaco, compared to other prehistoric settlements in the northern Southwest, is its stability and longevity. While most earlier (and, for that matter, later) villages were apparently only occupied for one or two generations, Chaco was a major center for at least 300 years, and may have been occupied at a lower level of population for another hundred or so years after the end of its regional centrality. Despite the apparent importance of this fact, however, it has received curiously little explicit attention in the scholarly literature on Chaco. This is probably because the stability of Chaco is easy to see but very difficult to explain. Any explanation will necessarily have to exist within a particular interpretation of what Chaco was, and given the enormous amount of dispute over that and the number of competing theories it’s hardly surprising that Chaco specialists have spent most of their time coming up with theories and arguing with each other, which has left little time for using those theories to specifically address the issue of stability. That is, all theories that have been proposed to explain Chaco contain implicit explanations for its stability, but explications of those theories very rarely address stability explicitly.
To some extent the explanation for Chaco’s stability depends on the exact nature of the Chaco system and the role of Chaco itself within it, which is a topic of considerable dispute among archaeologists, but there are also some more general factors that probably played a role in the unusual stability of Chaco.
The most important is probably the environment. The details are still a bit unclear, but it does seem from extensive research on the ancient climate that the rise of Chaco coincided with a period of unusually wet conditions that made farming more productive and reliable than it had been before in the arid Southwest. This would have made the accumulation of agricultural surplus easier than it had been before, which would in turn have increased the power and prestige of areas that were able to accumulate surpluses. This still doesn’t explain why Chaco specifically became so large and important for so long, since it’s not in a very productive agricultural area even by southwestern standards, but it may in part have just been a matter of fortuitous circumstance: Chaco happened to be where people were starting to gather, after leaving their earlier settlements elsewhere, when conditions improved and they were able to stay there longer than had been possible in other places before.
Another important factor was probably trade. Chaco isn’t in a very good place to farm, but it is located in a strategic position between the productive agricultural areas further north and the mountainous areas further south, each of which may have produced things the other may have needed. It’s not clear how much trade there was in things like agricultural products, which are rather difficult to transport over long distances without pack animals, but there was certainly a considerable amount of trade in pottery and valuable goods like turquoise, and Chaco is particularly known for the amount of material found there that originated elsewhere. Some theories have posited that Chaco was a center for redistribution of goods, but there isn’t much direct evidence for this and it’s hard to determine how much stuff passed through Chaco on the way to somewhere else (because that stuff wouldn’t have left any evidence of ever having been at Chaco). What is clear, though, is that whether or not substantial amounts of trade goods passed through Chaco, an enormous amount of important material came into Chaco and stayed there. Turquoise is the best known example, but there were a lot of other things too, including exotic goods like copper bells and macaws brought up from Mexico.
Whether from agricultural surplus or from trade, then, or possibly from both, Chaco was clearly a very wealthy place at its height, and it was probably that wealth that allowed it to last so long when other settlements had been so transient. Favorable environmental conditions probably played a role in the ability of Chaco to accrue that wealth, but not necessarily in a straightforward way. There may also have been other political, cultural, or religious factors that contributed to Chaco’s staying power. One thing that’s interesting to note is that while Chaco did last a long time, its end seems to have come pretty rapidly. Large-scale construction seems to have ended abruptly around AD 1130, and while a reduced population does seem to have remained in (or possibly returned to) the canyon until 1250 or so, the bulk of the population seems to have left for other settlements that ended up being occupied for much shorter periods. That is, Chaco was occupied much longer than earlier settlements, but also much longer than most later settlements. The fact that environmental conditions seem to have deteriorated as much at the end of the Chacoan era as they had improved at the beginning reinforces the impression that there’s some sort of relationship there.