This large, prehistoric pueblo community, trading center, and ceremonial site flourished circa 900-1180 c.e. The thirty-four-square-mile park contains one of the largest collections of ancient pueblo ruins in the southwestern United States. Chaco Canyon was the hub of a four-hundred-mile network of roads connecting it with numerous outlying communities, usually called outliers. The size and intricacy of its architecture, the sophistication of its agricultural irrigation system, and evidence of artistic, economic, and astronomical endeavors indicate this was an advanced ancient civilization, sometimes called the “Chaco Phenomenon.” Abandoned for unknown reasons in the twelfth century, its existence first became known to the outside world in 1849 when it was discovered by a U.S. Army expedition.

Site Office

Superintendent

Chaco Culture National Historical Park

P.O. Box 220

Nageezi, NM 87037

ph.: (505) 786-7014

Web site: www.nps.gov/chcu/

A millenium ago, an advanced civilization flourished amid the stark desert of Chaco Canyon in northwestern New Mexico. Its people were farmers, pottery makers, and sun worshipers, but above all they were builders. From 900 to 1115, the Anasazi (a Navajo word for “ancient ones”) created nine large multistory structures within the canyon, known as the Great Houses of Chaco, plus four more in the immediate area. The largest of these towns, Pueblo Bonito, had more than six hundred fifty rooms and covered three acres in a D-shaped structure. While there are numerous ruins of ancient pueblo dwellings throughout the southwestern United States, the Great Houses of Chaco were unusual because of their high ceilings, intricate masonry patterns, and sheer size.

Most of the construction at Chaco Canyon took place between 900 and 1115, with a sudden surge of activity starting around 1075. Construction of Pueblo Bonito, for instance, began in the early 900’s, but its east and west wings were added around 1075. These were massive projects, with construction of Pueblo Bonito’s east wing alone requiring an estimated 193,000 worker hours. About half of the work involved quarrying sandstone and cutting and transporting trees. Approximately 100,000 pounds of sandstone had to be cut by hand from the nearby cliffs to construct one small room; researchers estimate that one of the Great Houses, Chetro Ketl, required fifty million pieces of sandstone to be cut. Each of the Great Houses also required as many as 200,000 wooden beams for roof support. That the Chacoans were able to harvest sufficient trees for these projects is remarkable, considering that the nearest forests were at least twenty miles away.

The magnitude of these structures is reflected in early estimates of the peak population of Chaco Canyon. These estimates ranged from 4,400 to 25,000. Recent archaeological studies indicate that many rooms in Chaco’s structures were used for storage, not residential purposes, and the population probably never exceeded 2,000. Still, scientists believe there were more people than Chaco Canyon’s cropland could support. Numerous sites have been found where turquoise jewelry was made, suggesting that many Chacoans concentrated on craft work that they traded for food and other items brought into the canyon by others.

Besides large quantities of turquoise, excavations have uncovered painted black-on-white cylindrical vases, tools with inlaid decorations, drilled beads, rings, copper bells, and macaw skeletons. Scientists believe that the evidence of metal and macaws shows that Chacoans were trading with people far to the south, in what is now Mexico.

Chaco also was distinguished by a sophisticated agricultural irrigation system that captured and distributed the area’s scarce rainfall and an extensive network of roadways to connect the canyon’s villages with dozens of outliers. More than one hundred fifty Great Houses have been identified outside Chaco Canyon, connected to the canyon hub by numerous roads, usually from twenty-six to forty feet across, that run in straight lines for miles with only a few sharply angled “dogleg” turns. The existence of the roads has been known since the late nineteenth century, yet the full extent of the road system was not discovered until the 1970’s, when aerial photography was systematically used to find about four hundred miles of roads, only one hundred miles of which are inside the park.

These studies have illustrated that the Chaco culture extended well into what are now Arizona, Utah, and Colorado. Given the widespread nature of Chaco culture, some scientists believe that Chaco Canyon was much more than a place where people lived and goods were stored and traded.

Analyses of trash mounds at Chaco have found a huge amount of broken pottery, suggesting that breaking pots was part of some ceremonial ritual. Clear evidence of Chaco’s importance as a religious or cultural center is shown by numerous circular ceremonial chambers called kivas, including at least eighteen Great Kivas that measure up to 63.5 feet in diameter. These centrally located Great Kivas could accommodate dozens of people, perhaps even the whole town. There were dozens of smaller kivas, including at least thirty-two at Pueblo Bonito alone.

What the Anasazi built here during such a brief period was the center for what is often called the “Chaco Phenomenon,” an economic, social and religious system that extended far beyond the canyon and today’s park boundaries. The Chaco Phenomenon was the apogee of centuries of human life in the canyon, going back to nomadic hunters who roamed the area five thousand to seven thousand years ago. Around the first century c.e. the population grew larger and more stable as farming developed. By the 600’s and 700’s, a culture called the Basketmakers developed. These people were known for their basketweaving and pottery. A new pattern called the Pueblo culture emerged between 750 and 800; this was marked by flat-roofed homes made of mud, rock, and poles. As the population increased during the mid-900’s, the buildings became larger and more substantial, with masonry walls and underground kivas. By the late eleventh century, with such structures as Pueblo Bonito, Chetro Ketl, and Pueblo del Arroyo Chaco buildings had reached their maximum size.

Besides the more obvious large ruins, recent studies of the Chaco area have identified more than twenty-five hundred archaeological sites, ranging from prehistoric rock art to small, two-room structures. In the San Juan basin, at least sixteen thousand archaeological sites dating as far back as the Paleolithic era have been discovered, and some scientists believe that this area is the largest archaeological resource in the United States, with an estimated a quarter of a million potential sites. During the ten-year Chaco Project, an intense archaeological survey that ended in 1981, more than 308,000 artifacts were found. These artifacts included 255,000 pottery fragments, 2,254 stone tools, and more than 7,000 ornaments and mineral pieces.

By 1180, Chaco Canyon was largely abandoned, perhaps because of a lengthy drought. It was occupied briefly in the 1200’s by people from nearby Mesa Verde and reinhabited in the 1700’s by the Navajo, who remain in the surrounding area today. The site was marked on early Spanish maps, probably a mispronunciation of tse koh, the Navajo word for “rock canyon.” However, Chaco Canyon remained unexplored until its discovery in 1849 by Lieutenant James H. Simpson, a U.S. Army topographical engineer who was surveying Navajo country.

The first major excavations took place in 1896, led by Richard Wetherill, a one-time cow rancher turned archaeologist who discovered the ruins of Mesa Verde, Colorado, in 1888. Financed by Fred and Talbot Hyde, two wealthy New York brothers, Wetherill participated in the Hyde Exploring Expedition, which excavated 190 of Pueblo Bonito’s rooms over the next four years. Critics charged that the expedition had vandalized the ruins for profit, and the federal government ordered a stop to the excavation. It is unclear whether the charges were true, but the controversy resulted in passage of the Antiquities Act of 1906 to preserve Chaco and other ancient ruins. The following year, President Theodore Roosevelt signed legislation to establish Chaco Culture National Monument.

In 1921, the National Geographic Society sponsored the first major scientific investigation of Chaco, led by Neil M. Judd, curator of American archaeology at the Smithsonian Institution. He found that the Anasazi had built and rebuilt Pueblo Bonito several times over the years, with four distinct styles of masonry. This expedition also found that nearby Pueblo del Arroyo, 400 feet southwest of Pueblo Bonito, contained 284 rooms and 14 kivas. Pueblo del Arroyo’s masonry was similar but the handiwork and materials were inferior to its larger neighbor. “Pueblo Bonito stands today a fitting memorial to its unknown and long-forgotten inhabitants,” Judd wrote. “It stands a monument to their primitive genius, to their tenacity of purpose, to their ambition to erect a communal home in which each resident should find a deep and permanent interest.”

During the next forty years, many of Chaco Canyon’s lesser ruins were excavated, and a broader understanding of its culture developed. Sites that received attention included Chetro Ketl, a third giant pueblo near Pueblo Bonito. It is shaped like a capital letter E with a wall, now almost completely buried, enclosing the plaza within. Its longest side is more than 450 feet and its entire perimeter measures 1,540 feet. Like Pueblo Bonito, Chetro Ketl has intricate masonry, with layers of large stones alternating with small pieces to create a banded effect. One reason Chaco Canyon’s masonry is so distinctive is that it was made from a relatively hard variety of rock called Cliff House Sandstone, which could be chipped and ground with precision.

Within the plaza of Chetro Ketl, archaeologists found a huge Great Kiva, averaging 62.5 feet in diameter. It has been called the most important structure excavated north of Aztec Mexico. The base of a timber roof support was still in place, measuring 26.5 inches in diameter. This is the largest log ever found in Chaco, and its presence indicates a significant accomplishment, as the Chacoans had to transport it from miles away by hand. Archaeologists found that this Great Kiva had several more layers under the first terrace, with the original floor 12 feet below the top floor. At this level, they found ten sealed niches in the wall. Each contained turquoise pendants and strings of beads containing a total of seventeen thousand beads.

The largest Great Kiva is on the other side of Chaco Canyon. Measuring 63.5 feet in diameter, Casa Rinconada is the only Great Kiva that stands apart from any of the Great Houses or smaller structures. Archaeologists do not know whether it served the nearby villages or the entire canyon. Its most unusual feature was a 39-foot underground passageway leading into the chamber. This would have allowed participants in whatever rituals took place to enter the kiva without being seen by spectators.

A significant discovery in recent years is that the Chaco Anasazi developed a sophisticated solar calendar, probably for ceremonial and agricultural purposes. Known today as the Sun Dagger, it was discovered in 1977 by Anna Sofaer, an artist from Washington, D.C. Atop the 430-foot Fajada Butte near the park’s south entrance, she found three upright slabs of sandstone, about six to nine feet high, leaning against the cliff. These slabs allow sunlight to pass through in a vertical pattern. Behind them are two spiral petroglyphs (rock carvings) on the cliff; at summer solstice, she found that the narrow shaft of light bisected one spiral’s center precisely at noon. Other distinctive light patterns marked the equinox and winter solstice, and it is believed that the Sun Dagger also was used to predict lunar eclipses. Unfortunately, little more than a decade after its discovery, it became apparent the slabs had shifted, and the Sun Dagger no longer accurately marked the summer solstice. Visitors to the site may have caused erosion that allowed the slabs to move, and the site is now off limits to the public.

In 1980, after research showed the Chaco system covered a much larger area than originally thought, Congress passed legislation to protect thirty-three of Chaco’s outliers from the area’s extensive energy exploration and development. The bill also renamed the canyon and outlying sites as the Chaco Culture National Historical Park.

• Frazier, Kendrick. People of Chaco: A Canyon and Its Culture. Rev. and updated ed. New York: W. W. Norton, 1999. A thorough and highly readable review of Chaco Canyon’s ancient history through the eyes of archaeologists who explored its structures and complex social order.
• Lekson, Stephen H., Thomas C. Windes, John R. Stein, and W. James Judge. “The Chaco Canyon Community.” Scientific American, July, 1988. Worth reading for its illustrations, details, and insights is this article by four archaeologists who worked together for more than ten years studying Pueblo Alto and other Chaco Canyon Structures.
• Matlock, Gary. Enemy Ancestors: The Anasazi World with a Guide to Sites. Flagstaff, Ariz.: Northland, 1988. A more thematic approach is taken by Matlock. He covers the natural environment, culture, and history of the Chaco culture and provides information for visitors interested in serious appreciation of Chaco Canyon and other Anasazi sites in the area.