Great Drought of 1276: The Ancestral Puebloan Exodus

The Great Drought of 1276–1299 was a long dry spell in the American Southwest, first identified in the growth rings of ancient trees, that coincided with one of the largest population movements in pre-Columbian North America. In the last decades of the 13th century tens of thousands of Ancestral Puebloan farmers left the Four Corners region, including Mesa Verde, and moved south to new homes. The drought was a key part of that story, though not the only one.

Reading history in tree rings

The drought was discovered through dendrochronology, the science of dating with tree rings. Trees in dry climates grow wide rings in wet years and narrow ones in dry years, so a sequence of rings forms a pattern that can be matched between living trees and old timbers.

The astronomer A. E. Douglass, who worked in Arizona, developed the method in the early 20th century. For years he had two separate sequences: one running back from living trees, and a “floating” one from prehistoric ruins that could not be tied to calendar years. On 22 June 1929, a charred beam from a ruin at Show Low, Arizona, known as HH-39, bridged the gap. Overnight, the great houses and cliff dwellings of the Southwest could be dated to the exact year their timbers were cut.

Douglass also noticed a run of extremely narrow rings from 1276 to 1299 and called it the “Great Drought”. He announced the results in National Geographic in December 1929. Later studies, drawing on thousands of tree-ring samples across the region, have confirmed a severe and prolonged drought in this period, particularly in the northern Southwest.

The Four Corners before the drought

In the mid-1200s the northern San Juan region, centred on Mesa Verde and the Montezuma Valley in southwestern Colorado and southeastern Utah, was one of the most densely settled areas north of Mexico. Archaeologists estimate that the central Mesa Verde region alone was home to around 20,000–30,000 people.

They lived in villages of masonry rooms, many of them large and built around springs at canyon heads, and in cliff dwellings such as Cliff Palace at Mesa Verde. They farmed maize, beans and squash without irrigation, relying on rain and snowmelt. This dry farming worked well in good years but left people vulnerable to drought and short growing seasons at high elevation.

The region had faced crises before. An earlier drought in about 1130–1180 had helped end the dominance of Chaco Canyon and its network of great houses, and the population had shifted north into the Mesa Verde area.

A region emptied

The last tree-ring cutting dates from the Mesa Verde region fall around 1280. In the Kayenta area of northeastern Arizona, the cliff villages of Betatakin and Keet Seel were built in the mid-1200s and abandoned shortly after 1286. By about 1300 virtually no farming villages remained in the northern Southwest, an area of tens of thousands of square kilometres.

The migration was not a single event. People had already been leaving in smaller numbers from the mid-1200s, and the final departures probably took place over two or three decades. Families and clans moved in stages, sometimes stopping for a generation before moving on.

Why the people left

Researchers describe the causes in terms of “push” and “pull” factors.

Push factors:

• Drought. The Great Drought reduced harvests year after year, at a time when stored food could carry a family through one or two bad seasons but not many.
• Cold. Tree-ring and other evidence suggests cooler conditions in the late 1200s, shortening the growing season at higher elevations. Large volcanic eruptions, including the eruption of Samalas in Indonesia in 1257, may have contributed to cooling.
• Depleted resources. Centuries of farming, wood cutting and hunting by a large population had reduced firewood, game and soil fertility.
• Violence. At Castle Rock Pueblo in Colorado, excavations by the Crow Canyon Archaeological Center found remains of dozens of people killed in an attack around 1280. Defensive architecture and other sites with evidence of violence point to growing conflict.

Pull factors:

• New communities. Large villages were growing in the Rio Grande valley, around Zuni and Acoma, and on the Hopi mesas, where water and land were available.
• New religious practices. New forms of community ritual, including the spread of the kachina (katsina) religion in the 1300s, may have attracted migrants and helped integrate newcomers into large villages.

Most archaeologists now think the drought acted on a society already under stress, and that the attraction of the south was as important as the hardships at home.

Where they went

The migrants joined existing communities or founded new ones in the south and southeast. The 14th century saw the growth of large plaza-centred pueblos along the Rio Grande and its tributaries in New Mexico, at Zuni and Acoma, on the Hopi mesas and along the Little Colorado River in Arizona.

These are the ancestral homes of today’s Pueblo peoples. Tewa-speaking communities of the Rio Grande, the Hopi and others preserve oral traditions about ancestors who once lived in the north and travelled through many places before settling. In their view the movement was a purposeful migration, not a disappearance.

Archaeology supports links between north and south. Pottery styles, building techniques and the layout of villages in some Rio Grande communities show similarities with Mesa Verde traditions, and studies of ancient DNA and of skeletal features have been used to trace population movement, though the precise routes of individual groups remain debated. The newly enlarged villages had to integrate people of different origins, and plaza-centred ritual life may have helped to bind them together.

Lessons for the present

Because tree rings date the drought and the abandonment so precisely, the episode has become a widely studied case in research on climate and society. Projects such as the Village Ecodynamics Project, led by Timothy Kohler, Mark Varien and colleagues, have combined climate reconstructions, maps of thousands of sites and computer models to estimate how much maize farmers could grow in each year and place.

Their results suggest that the late 13th century was a period of unusually low and unpredictable farm production, but that people had survived comparable dry spells before. What made the 1270s and 1280s different was the combination of climate stress with a large population, conflict and the availability of attractive destinations elsewhere. Modern tree-ring studies also show that the Southwest has experienced so-called megadroughts several times in the past two thousand years, a finding that informs current planning for water supply in the region. Pueblo communities later endured Spanish colonisation and rose against it in the Pueblo Revolt of 1680.

Timeline

• c. 1130–1180: An earlier drought contributes to the decline of Chaco Canyon.
• c. 1190–1260: Population peaks in the Mesa Verde region; cliff dwellings are built.
• 1257: The Samalas eruption in Indonesia, one of the largest of the last millennium.
• 1276: The Great Drought begins.
• c. 1280: Last tree-ring cutting dates at Mesa Verde; violence at Castle Rock Pueblo.
• c. 1286: The Kayenta cliff villages of Betatakin and Keet Seel are abandoned soon after.
• 1299: The Great Drought ends.
• 22 June 1929: Beam HH-39 allows A. E. Douglass to date Southwestern ruins precisely.

Why it matters

The Great Drought and the Ancestral Puebloan migration are among the best-documented cases of how climate and society interact, dated to the year by tree rings. They show that people facing environmental stress make choices shaped by their social world, and that migration can be a strategy for survival and renewal rather than a story of collapse.