Oak trees grew in abundance along low-elevation, permanent streams and provided the staple food of acorns, which were used to make cakes and bread. Native Americans ground acorns into a fine mush using holes in the local granite bedrock as mortars. Permanent winter settlements in the foothills consisted of pit houses thatched with tules (vast amounts of which once grew in the marshes of the Kaweah delta) up to in diameter. Hospital Rock, a flat next to the Middle Fork, was used as a camp possibly as early as the 1300s AD.