The cultivation of corn first began appearing in the American southwest around 2000 BCE, some seven thousand years after the crop was first cultivated in southern Mexico. Being a tropical plant, it took some time to selectively breed varieties better able to survive in the deserts of northern Mexico and the American southwest. Native Americans in the area planted corn along river and creek bottoms, but retained a hunter gatherer lifestyle. This was due to the fact that eating mainly corn resulted in a disease called pellagra, a niacin nutritional deficiency which could cause death. This was not as much of an issue in Mesoamerica, where the nutrients found in squash and beans could make up the difference, but both of these crops required more water than was available. This hybrid lifestyle largely remained unchanged until around 0 CE, when the nixtamalization process was introduced from southern Mexico, which is just a fancy word for soaking corn in water with ash in it to free up otherwise undigestible nutrients. How in the hell anyone figured such a thing out is unknown, but it most definitely worked. Corn became a much more viable part of people’s diets and societies based around agriculture began to take shape.
The three largest of these new southwestern societies were the Hohokan in the west, the Mogollon in the east and south, and the Pueblo in the north. These societies quickly began to dominate and assimilate the tribes around them, over time growing in size to cover significant portions of the southwest. Though differing in language and culture, when coming into contact with each other they remained largely peaceful, exchanging and spreading ideas such as architecture, pottery, and ceramics. By 500 CE, these societies began developing widespread irrigation projects, allowing for the cultivation of squash and beans. Along with corn, these two crops became known as the three sisters. When planted in the same field, the bean vines could climb the corn stalks and the leaves of the squash would shade the soil, retaining water and preventing weeds from growing. The three sisters allowed the three societies to shift almost entirely to agriculture, which in turn led to them building permanent settlements using mud bricks.
Over the next several hundred years, irrigation projects were expanded and made more intricate, including the construction of dams and reservoirs, and settlements turned into cities, some populated by several thousand people living in multistory communal dwellings. Regular trade with tribes in northern Mexico created a conduit to the major civilizations of Mesoamerica, allowing for the importation of such luxuries as domesticated turkeys, copper bells, mosaics, stone mirrors, and macaws. Other ideas moved north as well, such as religious ideas based upon the worship of the natural forces which could bless or curse crops, but luckily not the Mesoamerican penchant for human sacrifice to appease such forces. Another idea that came north was the focus on astronomical observation, with temples built to track the movements of the heavens. An upper class of appointed chiefs and religious leaders formed. Populations expanded rapidly, thanks both to larger families becoming more common and the migration and assimilation of outsiders looking for a better way of life.
Unfortunately, it was not to last. A relatively warm climate with adequate consistent rainfall began to shift around 1150 CE, entering into a three hundred year period known as the Great Drought. Weather became less predictable. Summers became hotter and drier, making it more difficult to grow crops, and winters became colder and wetter, resulting in floods which damaged the intricate irrigation networks. Soils became depleted of nutrients, forcing many settlements to be abandoned or moved, which sparked conflict as people were faced with the need to defend their still fertile lands or face starvation. The three societies were not the only ones affected. Many of the tribes in northern Mexico began migrating towards more fertile lands to the south, effectively cutting off trade with Mesoamerica. In the north, the hunter gatherer Numic peoples, who inhabited the Great Basin, unable to forage enough food, began raiding the Pueblo, many of whom began moving south into the territories of the Mogollon, sparking further conflict. As a result, many settlements began being built into the sides of cliffs and protective adobe walls were built. Peaceful co-existence was no longer an option.
By 1300 CE, the three societies were in a state of collapse. Infrastructure was in disrepair and what viable fertile land was still available was quickly being over farmed, with many communities being forced to move every thirty years. This was only made worse by the need for defense leading to the abandonment of smaller settlements in favor of larger ones. In the midst of this chaos, a religious movement began to sweep the region, one claiming the cause of the drought was their ancestors hubris in becoming too spiritually powerful. To return the world to balance, the temples with their precise astronomical measurements were sealed up or destroyed, and some evidence exists of even human sacrifices or cannibalism occurring. As conflict over limited resources intensified, many of the cliff dwellings were abandoned in favor of more easily defended new settlements on top of mesas. The final nail in the coffin came around 1400 AD, when the Na-Dene migrated into the area from the Pacific Coast, laying claim to wide swaths of land formerly controlled by the three societies.
The end of the Great Drought around 1450 CE finally allowed the situation to stabilize. The most negatively affected group was the Hohokan, their people scattered into small tribes which coalesced into the Hopi and the Zuni. In comparison, the Pueblo society and culture remained more intact. Pushed south deeper into New Mexico, they largely assimilated the Mogollon over the course of the Great Drought, becoming the last major remnant of the original three societies. As for the Na-Dene that entered the area, they split into two different groups. The Navajo adopted a more agricultural society similar to the original inhabitants, setting up shop in northern Arizona and New Mexico. Over time they became closely tied to the Pueblo, becoming quite similar to them culturally. In comparison, the Apache retained their migratory hunter-gatherer lifestyle. Belligerent to outsiders, and without anyone to stop them, they laid claim to wide swaths of territory across New Mexico and Arizona. Though willing to trade when it suited them, they were not opposed to raiding their neighbors as well.
