5. Habitat areas 7A-14: the northern Yokuts, central and northern Miwok 77 6. The Lower San Joaquin River and Delta areas 78 THE ABORIGINAL POPULATION OF THE SAN JOAQUIN VALLEY, CALIFORNIA BY S. F. COOK INTRODUCTION Ecologically the great central valley of California forms a single unit. Nevertheless it is convenient for the purposes of this paper to divide the entire area into two portions, north and south. The vast expanse from Red Bluff to the Tehachapi is too extensive to cover demographically in a single exposition. Moreover, the northern tribes, the Wintun and Maidu, are physiographically clearly segregated from the southern by the northern extension of San Francisco Bay and the delta of the rivers. Hence we shall consider here only those peoples south of the Sacramento and American River watersheds. The area possesses definite natural limits but its exact boundaries must be to some extent arbitrary. On the north the line has already been indicated: the south bank of the upper Bay and the Sacramento River as far upstream as a point five miles below the city of Sacramento and thence easterly along the El Dorado--Amador County line into the high mountains. This follows Kroeber's tribal boundary between the Maidu and the Sierra Miwok. On the west the line starts northeast of Mt. Diablo and follows the western edge of the San Joaquin Valley to the Tehachapi Mountains. On the east we include the Sierra Nevada as far as was reached by permanent habitation on the west slope. The southern extremity is represented by the crest of the Tehachapi. The region designated embraces the territory of the Plains and Sierra Miwok, the Yokuts, the Western Mono, the Tubatulabal, and the Kawaiisu. From the standpoint of habitat the area is diversified since it extends from the swampy valley floor through the oak country of the lower foothills into the transition life-zone of the middle altitudes. Perhaps an ecological segregation would be desirable. Such a procedure, however, would cut across tribal boundaries and make an accurate evaluation of population difficult. On the accompanying maps, areas are delineated, and numbered, primarily for convenience of reference. At the same time they conform as closely as is feasible with the natural subdivisions of the territory marked out by river valleys, lakes, plains, and mountains. It should be stressed that they do not necessarily coincide precisely with the areas occupied by specific tribes or groups of tribes.