Pueblo Bonito is the largest of the Great Houses in Chaco Canyon. It was constructed in four phases starting at about 900 and ending by about 1115. This pueblo still stands four stories high at the back, once had a fifth level, and contained between six and eight hundred rooms and about forty kivas. Several Great Kivas are located within its huge plaza, split in two by a long, low building. The Chacoan method for building large, multi-storied houses was employed where the great weight of the upper stories was supported by massive walls in the lower levels. (view from the air is from National Geographic, November, 1982)
With such techniques as tree-ring dating, (dendrochronology), the analysis of masonry styles and ground plans, it has been determined that Pueblo Bonito went thru four distinct construction phases: 900s-1020; 1020-1050; 1050-1075; and 1075-1115. The way walls are joined is another method for identifying construction sequences. Walls that join in a flushed, "abutted" manner were constructed at different times which with stones interconnecting at corners were usually built at the same time. In keeping with the Chacoan trademark of pre-planned design, this staged expansion over multiple generations achieved its most elaborate and lengthy time-duration form in Pueblo Bonito.
After the pueblo was abandoned in the 1100s, the upper walls collapsed thus making it impossible to know the exact maximum number of rooms created although the figure of 800 has been posited. Also, over time, many of the older rooms were filled in to then act as footings for the upper levels that extended to five stories along the rear wall. Some estimates are that no more than 600 rooms were ever in use at one time. Thirty-seven kivas of varying sizes have been located throughout Pueblo Bonito, but, as with the other rooms, not all were apparently in use at the same time.
There are four distinct types of masonry at Pueblo Bonito that evolved over centuries. The oldest walls : the oldest, commonly referred to as Type I, employed sandstone slabs, 2 lying side-by-side per layer, held together with mud-and-sand mortar. Type I walls required more maintenance than later types because the mud joints were larger and, when exposed to the elements, it was necessary to regularly repair mortar damage to maintain the walls. The second type, called Type II, used hand carved sandstone blocks with thin laminate sandstone tablets in taking up the space between the larger blocks. The third kind of masonry wall, called Type III, is a core-and-veneer structure with a core, consisting of roughly-shaped stones and rubble laid flat in adobe (mud) mortar, surrounded on both sides of the visible wall with carefully shaped stones forming a veneer, which in Type III usually has the appearance of thicker rows of sandstone blocks interspersed with rows of thinner sandstone. The fourth distinct walls, called Type IV, were also of core-and-veneer structure, but the veneer now consists of sandstone tablets of uniform thickness in each row. The precision and smoothness of wall edges and door corners, in Pueblo Bonito especially (although this is true throughout Chaco Canyon to varying degrees), is even more wonderous considering the apparent fact that the people who built these architectural wonders had no written mathematics.
The differing significance of the four Types of masonry styles is not known. Most explanations for variations in masonry styles concede the most straight-forward reason being that individual stone masons had different preferences and artistic inclinations. Every phase of Anasazi culture manifested it's own particular form of basketry, pottery, masonry, and architecture. The exquisitely precise and close-fitting Chacoan masonry is an instance of the development of a particular style.
Pueblo Bonito is a wonderous architectural achievement created by a people who apparently did not possess metal tools, the wheel, or any beasts of burden. Pueblo Bonito embodies the Great Houses trademark manifest throughout Chaco Canyon, and, to differing degrees, the Southwest in general: elegant masonry structures, two or more stories high with the highest floors constructed to the rear, and generally to the north side of the pueblo; building on a massive, pre-planned-design scale; south facing and terraced to maximize solar gain; subterranean chambers called kivas located both in the roomblocks as well as in the plaza area, but always in front of rooms; and storage rooms built on the back side and in lower-floors, while the living quarters faced the plaza. At the south edge of the plaze a row of rooms was constructed separating the plaza itself from a trash dump. As was the case at Chetro Ketl, the presence of great kivas, signifies the size and importance of these buildings. Such kivas were the ceremonial centers of these Pueblos and may have served outlying villages and habitations as well.
Pueblo Bonito was the largest of the Great Houses in Chaco Canyon. The people who lived here were members of a farming community incorporating housing, work areas, clan or lineage group kivas, and great kivas. The abundance of evidence of community endeavor in the form of roadways, water channeling and irrigation systems, communications systems, and the solar observatory on Fajada Butte, indicate Pueblo Bonito was part of a much larger social entity.
WUPATKI MESA VERDE AZTEC CHACO CANYON