The question of Chaco Canyon timbers

Some 1,000 years ago, a group of Ancestral Puebloans camped in a pine forest. They were part of an organized labor force focused on a singular task—harvesting trees that would be used to build the spectacular buildings of what we now call Chaco Culture National Historical Park in northwestern New Mexico.

Workers used stone axes to pummel away (not cut, as with metal axes) at the base of trunks until the trees could be tipped over. Then a crew stripped the bark and branches, while roughly shaping the log into a long, straight timber.

All told, these crews harvested at least 240,000 trees over a 300-year span. Many of the Chaco Canyon timbers were huge: Primary roofing beams averaged 8 to 10 inches in diameter, 15 feet long, and several hundred pounds.

But forests containing long, straight trees did not grow anywhere near Chaco Canyon during the last several thousand years. And there were no draft animals, wheeled vehicles or navigable rivers to assist wood transport. Archaeologists
have long wondered: Where did this wood originate—and how did Ancestral Puebloans move such massive timbers?

Given the epic scale of Chacoan construction, answers to these questions have implications for understanding Ancestral Puebloan social organization a millennium ago.

A UNESCO World Heritage Site, Chaco Canyon is a remarkable place. There, in a mile-high desert, one of North America’s most complex societies flourished for three centuries, from roughly C.E. 850 to 1150. The most visibly striking features of Chaco Canyon are the remains of
as many as 12 magnificent structures that archaeologists call “Great Houses.”

To build the structures, Ancestral Pueblo people needed wood, sandstone blocks and mud mortar. Two of those ingredients—sandstone and mud—were literally under their feet. The surrounding landscape, now called the San Juan Basin, bears abundant sandstone formations, which provided tens of millions of small, flat blocks used for Chacoan buildings.

But the Great Houses also required hundreds of thousands of wooden beams—and the ideal trees did not grow locally. Although pinyon pine and juniper trees dot the San Juan Basin, those species tend to sprout chaotically, often with multiple stems and twisting branches. They rarely grow straight enough to yield quality timber for rectangular rooms in large, multistory buildings.

Smithsonian