Chaco Canyon

c. 900 CE — North America, Ancestral Puebloans

Today: Northwestern New Mexico, USA

In a dry canyon in New Mexico, Ancestral Puebloans built great houses of hundreds of rooms — the largest, Pueblo Bonito, rose four storeys and stood as the biggest building in North America until the 1800s. Dead-straight roads ran for miles across the desert to nowhere in particular, and timber for the roofs was carried from mountains fifty miles off, without wheels or draft animals. Macaw feathers and cacao from Mesoamerica turn up in the ruins. A fifty-year drought after 1130 emptied the canyon.

Worth knowing: Chaco's buildings track the sky: windows and walls align with the solstices, and one great house aligns with the moon's 18.6-year standstill cycle — which takes generations of observation to even notice, let alone build for.

Pattern: Environmental & resource stress — An environmental shift (drought, cooling) strains food and water systems, amplifying every other tension at once.

Entry 109 of 240 in Precedent, a walk through the whole human story in order.