Siplichiquin Shell Mound
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Siplichiquin Shell Mound


Siplichiquin Shell Mound
Large shellmound with a bay view
Elevation 30 ft.

Subsurface charcoal samples recovered here have been radiocarbon dated back over 5,000 years, making this shellmound one of the oldest in the Bay Area. Other charcoal samples date from just a few hundred years ago. Perhaps this mound was an active village site when the Spanish first colonized the San Francisco peninsula.

Looking down on the shellmound from the slopes of San Bruno Mountain with San Bruno Point and San Francisco International Airport in the background. The shellmound lies under the triangular patch of yellow weeds adjacent to a willow grove right off Bayshore Blvd. and U.S. 101.


In 1909 N. C. Nelson published Shellmounds of the San Francisco Bay Region, which included a map showing the location and degree of preservation of 425 “shell heaps.” The Siplichiquin mound was represented as being “partially present” on Nelson’s map. Bob stands on the shellmound, as does the photographer, below its highest point. In its aboriginal state the mound would have sloped gradually toward the bay. Evidently it was excavated before 1909, perhaps during construction of the San Bruno Turnpike in 1858. We estimate its pre-excavation size as 75 yards long, 30 yards wide, and 6-8 yards deep.


The grey soil of the mound is full of shells and feels spongy when walked on. No wonder road contractors prized it as ballast for their roadbeds.


Shells from some of the bivalves consumed here. The shells were returned to the mound after being photographed.


We don’t think this is a prehistoric tsektsel (prayer seat), but it sure is a great place to take in some fabulous views.