More Information on the Indians of Suisun Valley
Bedrock Mortars for Grinding Acorns. Bedrock Mortar Sites. Bedrock mortar sites are also called quot;milling stationsquot;, and they are where long ago the Indians of California ground up acorns, which were one of the main items of their diet. The mortars they left behind are actually manmade holes, which were ground and pounded into rock slabs and boulders using stone tools called pestles.