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Simone Mound was one of the last undeveloped parcels in a growing residential area. The acquisition and preservation of this unique California mound site offers future researchers a rare opportunity to understand ancient Bay Area inhabitants and their culture.  

California | Despite limitations associated with the pandemic and the subsequent shutdowns, The Archaeological Conservancy recently completed two acquisitions in the Western Region. Both properties required lengthy planning and negotiations that spanned over years. Each site offers important information about the prehistory of California and the Native Americans who occupied the area hundreds and thousands of years ago.

In Part 2 of this series, The Conservancy’s Western Regional Director, Cory Wilkins, shares details about Simone Mound, one of the few mound sites remaining in the Bay Area.  The site was once occupied by early hunter-gathers who left behind earthen mounds comprised of refuse, soil, artifacts, and burials.  

The Acquisition of Simone Mound in Oakley, California

By Cory D. Wilkins, Western Region Director

The San Francisco Bay Area supported a dense population of hunter-gatherers over thousands of years leaving a rich and varied archaeological record. The Bay Area was a place of incredible language diversity with seven languages spoken at the time of Spanish settlement in 1776. The diverse ecosystem and abundant resources of the bay and surrounding lands supported an average of three to five persons per square mile.

When the Spanish arrived, the people of the Bay Area were organized into local tribelets that defended fixed territories under independent leaders. Bay area tribelets were thought to include 200 to 400 people distributed among three to five semi-permanent villages existing within territories measuring approximately 10 to 12 miles in diameter*. The activities of daily life in these villages resulted in mounds of refuse and soil that are still visible today. It is estimated that the San Francisco Bay Area and Sacramento Delta region contained well over 400 hundred mounds sites.

View of Simone Mound from Roadway

Unfortunately, many of these sites have been destroyed by urban encroachment and few remain. The Archaeological Conservancy recently acquired one of these unique sites. CA-CCO-139, more traditionally known as Simone Mound, is one of the last undeveloped parcels in a growing residential neighborhood. The site is on 5.95 acres just outside of the city of Oakley, California near another and similar Conservancy preserve, the Hotchkiss Mound.

Dr. Jelmer Eerkens collecting research data at Hotchkiss Mound site, which is near the recently acquired Simone Mound.

The mounds were created through daily activities such as processing shellfish, manufacturing stone and bone tools, cooking, butchering game animals, and building shelters which led to the accumulation of shells and other material. Generations of native peoples returned to these mounds throughout the centuries, using the sites for habitation and as burial grounds for their ancestors. Archaeological research has uncovered a variety of shell beads, charcoal, shells from native shellfish, stone tools, animal and fish bone, and other faunal artifacts. Much can be learned about the inhabitants of these mounds through the analysis of these stratigraphically preserved items.

Shell fragment left behind by the inhabitants of Simone Mound.

Previous research suggested that the Hotchkiss and Simone mounds were occupied concurrently. However, in 2013, Dr. Jelmer Eerkens and Dr. Eric Bartelink found evidence that the sites may have been occupied sequentially. The team performed Accelerator Mass Spectrometer (AMS) analysis on previously collected bone fragments to establish a chronology for the sites. The results indicate that as occupation at the Simone Mound was winding down, the Hotchkiss Mound saw its first interments. This suggests the inhabitants may have simply moved from one mound to the other. Burials from Simone Mound date mainly to the Middle (200-1000 AD) and Middle/Late Transition (1000-1250 AD) periods, while burials from Hotchkiss are just beginning during the Middle/Late Transition. The majority of Hotchkiss burials date to Phases 1 and 2 of the Late Period (1250-1750 AD). What was surprising is that there was no overlap in the distribution of the dates between the sites, offering clear evidence for sequential occupation. Together with changes in mortuary customs, this research suggests a major cultural shift during the middle of the Middle/Late Transition period.

An obsidian flake found on the surface at Simone Mound.

Further research will be necessary to determine why a large mound, such as Simone, was suddenly abandoned and never reoccupied during the Late Period. Alternative theories propose that the Hotchkiss people may have suffered a traumatic event such as disease, violence, or flooding that would have made their previous location uninhabitable; or Simone belonged to a different cultural group altogether**. It is possible that Late Period occupation is present at the Simone Mound; however, evidence for this may be spatially separated from the previously excavated areas. Further investigation is needed.

The Conservancy’s acquisition of the Simone Mound will preserve the site for this important future research and protect the site from being destroyed by development and agricultural activities like so many other mounds sites have. Combined with Hotchkiss Mound, these sites offer a wealth of information on the ancient past of the Bay Area, as well as unique research opportunities that have been largely ignored in the past.

Simone is one of the last undeveloped parcels in this residential neighborhood. Many other sites like Simone have been swallowed up by encroaching development.

* Milliken, Randall 2007. Punctuated Culture Change in the San Francisco Bay Area, In Prehistoric California: Colonization, Culture, and Complexity, edited by T.L. Jones and K.A. Klar, 99–124. AltaMira Press.
** Jelmer W. Eerkens & Eric J. Bartelink. 2019. New Radiocarbon Dates from
CA-CCO-138 (Hotchkiss Mound) and CA-CCO-139 (Simone Mound) and Insights into Mounds, Settlement Patterns, and Culture History in the California Delta, California Archaeology, 11:1, 45-63, DOI: 10.1080/1947461X.2019.1581979

The Archaeological Conservancy (2020) /