A survey of the central San Joaquin Valley has demonstrated a threefold cultural sequence north of Stockton, upsetting the earlier view that central California archaeology lacked evidence of change; south of Tulare Lake are indications of similar cultural stratification. Before the survey the 160 miles between Stockton and Tulare Lake was known only from scattered specimens and occasional correspondence with local collectors. The area of the 1939 reconnaissance is bounded on the north by the southern limit of Schenck and Dawson's 1929 report, the Mount Diablo Base Line; on the south, by Gifford and Schenck's northern limit, the southern end of Tulare Lake; on the east and west, by the Valley drainage limits. This territory includes the basin of the second largest river in California, and was formerly occupied by the bulk of the Yokutsspeaking peoples, and by some of the Miwok and Mono.