California Code, Government Code - GOV § 25363

The board of supervisors may sell or lease at public auction, and convey to the highest bidder, for cash, any property belonging to the county not required for public use.  The sale or lease may be made at the courthouse door or at such other place within the county as the board orders by a four-fifths vote.  Notice of the sale or lease shall be given for five days prior thereto either by publication in a newspaper published in the county or by posting in three public places in the county.  The proceeds shall be paid into the county treasury for the use of the county.  If in the unanimous judgment of the board, the property does not exceed in value the sum of five hundred dollars ($500), or the monthly rental value thereof is less than seventy-five dollars ($75), or if it is the product of the county farm, it may be sold or leased at private sale without advertising by any member of the board authorized by a majority vote of the board.  The sale or lease shall be reported to and confirmed by the board.  This section does not apply to the furnishing of goods to special districts.