Why Build Mounds?

An enormous amount of labor went into the construction of platform mounds. Adobe walls were built to form cells that were then filled with dirt and rocks. Residential, ceremonial, and storage rooms were built on top of, and around the mounds. Mound-top rooms required extensive labor and nearly ten times more material than ground-level rooms.

Why did people across south-central Arizona build mounds? There are many theories:

• O’Odham oral tradition holds that mounds were the homes of priests who had leadership roles and religious power.
• Some archaeologists propose that elevated mounds and the surrounding walls may have played a role in defense of the sites.
• Research shows evidence of flooding in some areas. The elevated mound areas may have provided a dry place for storage of goods.
• Mounds may have had ideological or symbolic significance. Some pyramids in Mesoamerica, for example, represented mountains from which water was believed to originate.

Two settlement Complexes: Platform Mounds and Mound Villages

Recent excavations in the Tonto Basin uncovered at least two architectural styles in the “urban centers” of the late Salado Horizon. Both included rooms built on top of and around elevated adobe mound structures.

• Platform mounds, in the west Basin, exhibit a formalized rectangular structure with walls restricting access to the mound area. They are similar to Hohokam mounds like Pueblo Grande, located in the city of Phoenix.
• Mound villages, in the east Basin, contained irregularly shaped elevated mounds with little access restriction. They are similar to Pueblo villages, with the addition of an elevated mound area.

Tonto Basin settlements in the late Salado horizon were comprised of small communities organized around these two types of urban centers. The examination of room use indicates that these mound centers were home to privileged groups who administered ceremonial, and in some area, economic aspects of life in the Basin.

Platform Mounds: West Tonto Basin Ceremonial Centers

• Large rectangular elevated mounds, built by the surrounding communities.
• Compound wall restricted mound access.
• Few residential rooms.

Platform mound communities were comprised of a complex of neighboring settlements extending up to three miles along Tonto Creek. Construction of the “community center” platform mound required the efforts of the entire settlement complex. Residents of the complex likely cooperated in the planning and construction of canal systems as well. The people of these settlement complexes may have viewed themselves as members of a single group.

Platform Mounds:

• Only a few families (7-9) resided at the mound, and probably held special status within the community complex. They may have been representatives of lineage groups within the community, possibly responsible for the ceremonial duties of that lineage.
• Access to the mound was restricted by a compound wall. Residences at the mound included food preparation and storage rooms. Mounds also housed stored food supplies sufficient for hosting feasts for the community complex. Special rooms, large enough for gatherings, contained special artifacts like unusually shaped stones, and were identified as ceremonial rooms.
• The amount of stored foods was not sufficient for redistribution to the surrounding settlement complex. There was no evidence of especially large stockpiles of raw materials or finished craft items. This indicates that mound residents did not control trade, production of craft items or food supplies.

These findings indicate that platform mounds were used as gathering places, with high status residents organizing feasts and other ceremonies. Ceremonial functions, centered at platform mounds, may have served to tie a cooperative group together.

Recent excavations document another settlement type, called mound villages, in the Tonto Basin during the late Salado Horizon. If the two settlement types were contemporary, the variation may reflect the mix of local and non-local groups who inhabited the area throughout its history.

Mound Villages: East Tonto Basin Ceremonial and Economic Centers

• Small irregularly-shaped mounds, built by the mound residents.
• No restricted mound access.
• Many residential rooms.

Mound villages appear somewhat different from platform mounds in architecture and function. These mounds were not as formal in design and there were no compound walls to restrict access to the mound. The mound residents could have constructed the mound; efforts of the surrounding settlements were not required.

Many families (25-30) resided at the mound village. Unlike platform mound residents, they were probably not representative of lineages living in neighboring settlements. The mound village was the largest and most successful settlement within a group of neighboring communities.

Mounds included food preparation rooms and enough storage space for abundant food surpluses. Mound village residents may have controlled the most fertile lands. Surrounding villages, on less fertile land, may have relied on mound village surplus food.

The mound village appears to have functioned as an independent community, perhaps hosting feasts for the surrounding settlements. These ceremonies were probably held in large outdoor plazas. Ceremonial items were found within residential areas, and no large separate ceremonial rooms were identified at mound villages.

Interpreting the Evidence

Less structured and less restricted ceremonial spaces may represent a less formalized ceremonial system than existed at platform mounds. Abundant stocks would have allowed the mound villages to host frequent ceremonies and feasts. Mound villages appear to have played a role in both ceremonial and economic functions within the community complex. Excavations document two settlement types, mound villages, and platform mounds, in the Tonto Basin during the late Salado Horizon. If the two settlement types were contemporary, the variation may reflect the mix of local and non-local groups who inhabited the area throughout its history.

Where Did They Go?

Tonto Basin population grew steadily through the 14th century, with people aggregating into ever larger villages. Why were these villages abandoned by AD 1450? Several theories have been proposed:

• Some research indicates that environmental catastrophes -- cycles of drought and flood – severely affected agricultural production.
• With an influx of people from other areas, the Basin’s population may have become too large to be sustained.
• Some researchers propose that conflict among groups in or outside the Basin may have contributed to the area’s abandonment.

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