Cal. Welf. and Inst. Code § 10800
Subject to the provisions of Section 11050 and Chapter 3 (commencing with Section 12000) of Part 3, the administration of public social services in each of the several counties of the state is hereby declared to be a county function and responsibility and therefore rests upon the boards of supervisors in the respective counties pursuant to the applicable laws, and in the case of public social services for which federal or state funds are provided, subject to the regulations of the department and the State Department of Health Services.
For the purpose of providing for and carrying out this function and responsibility, the board of supervisors of each county, or other agency as may be otherwise provided by county charter, shall establish a county department, unless otherwise provided by the county charter. Except as provided herein, the county department shall be the county agency for the administration of public social services and for the promotion of public understanding of the public social services provided under this code and the problems with which they deal.
Ca. Welf. and Inst. Code § 10800