Chaco Canyon: Anasazi Culture
by Peggy Gaudy, US Bureau of Land Management Archaeologist.
Appears by permission.
Chaco Canyon was both the political and economic center of the eastern Anasazi world by AD 1000. Within the canyon an architectural style consisting of very large, multi-storied pueblos and associated earth-works had been started and continued to grow in both size and number. These Chacoan structures were pre-planned, had large rooms, high ceilings, enclosed kivas, associated great kivas and core-and-veneer masonry. The Chacoan structures are up to four stories high with 695 rooms.
The wall height necessitated the use of core-and-veneer walls. The walls were over four feet wide at ground level, tapering at higher stories. The characteristic Chacoan veneer was constructed of sandstone blocks and slabs that were often pecked and ground to shape. A unique patterns of rows with larger, then smaller stones are visible in many of the walls.
Wood was a scarce resource in Chaco Canyon and the near by regions. Thousands of pine and fir logs were carried by hand up to 50 miles for the celing and roof construction. Subterranean kivas located within the roomblocks or enclosed plazas have been referred to as ceremonial rooms. Recent research indicates they may have been multi-functional. Pueblo Bonito, one of the largest ``great houses'' in Chaco Canyon, contains 33 kivas and three great kivas. Also constructed were isolated great kivas such as Casa Rinconada and smaller habitation sites.
Extensive petroglyph panels were etched, scratched, and ground on the soft sandstone canyon walls. Images of animals are common. The most famous petroglyph is the spiral associated with the "sun dagger" on Fajada Butte. During the solstice a ray of light shines through detached sandstone slabs, creating a ray of sun across the center of the spiral.
Radiating from Chaco Canyon were a series of prehistoric "roads" tying Chaco Canyon to sites spread across the San Juan Basin and surrounding areas. These sites appear to be the result of a spreading of "Chacoan" architectural pattern outward from Chaco as "...existing communities adopted an overlay of Chacoan architectural traits, while maintaining an otherwise local architectural and material culture." 
Over 80 Chacoan outliers have been recorded ranging in size from less than ten to over 100 rooms. The roads were constructed to a uniform width of approximately 30 feet and are almost always perfectly straight. If a slight change in direction was necessary it was never gradual, rather a "dog-leg" was constructed in the road. Research reveals the roads were maintained throughout their use.
Although construction and major occupation of Chaco Canyon ended about AD 1130, the Chacoan Anasazi continued to flourish in the surrounding areas. It appears that the center of the sphere of influence moved north from Chaco Canyon to the lower La Plata, Animas, and the San Juan Rivers. Aztec, Salmon, and other sites along the San Juan, Animas and La Plata Rivers became the focus of religious and possible economic activities. In other portions of the San Juan Basin and surrounding areas Chacoan structures were either abandoned or remodeled.