Recent excavations at the Cross Creek site (CA-SLO-1797) on the central coast of California revealed a stratigraphically discrete midden component dating between ca. 8350 and 7700 cal B.C., making it the oldest mainland shell midden on the west coast of North America. A large recovery volume revealed an assemblage dominated by grinding implements (handstones and milling slabs) and crude core and flake tools typical of California's Milling Stone horizon, but the Cross Creek findings extend the antiquity of Milling Stone back to the terminal Pleistocene. The tools and associated faunal remains suggest a gathering economy profoundly different from the terminal Pleistocene big-game hunting of interior North America. This variation is difficult to reconcile as a simple adaptive outgrowth from late Pleistocene hunting and may reflect a separate coastal migration route into the New World.