Native Americans are understood to have used this large rock for preparing food by pounding or grinding acorns, nuts, or grains, and the several holes in it reflect long-term use over many generations. The rock may have stood near Native American encampments by the mouth of nearby Clear Creek, where abundant salmon runs gathered and provided an attractive food source. During fall encampments, when acorns and other grains of the Willamette Valley were harvested, women dried the acorns in the open air and then pounded them into meal in holes like these to make soup or mush, using the rock as a mortar with a stone pestle. Some prefer the term "pounding rocks" rather than "grinding rock," while others call such features "bedrock mortars." No other evidence of Native habitation has been discovered on this historic site. Close by, a trail to the river later became the wagon road to Horace Baker's slack-line ferry, and evidence of that road remains along the hillside just inside the tree line from the shed to the Pioneer Church. Beyond the rock, a branch trail now leads to the restaurant and up to the cliff face, where several quarried rocks still show evidence of drilling and cleaving.