This collection contains official records created or commissioned by the Sonoma County Board of Supervisors, including records of special districts in Sonoma County. Some records jointly created by the Sonoma County Administrator's Office.

This collection contains records created by the Sonoma County Clerk-Recorder-Assessor-Registrar of Voters and its preceding offices, including the Offices of the Clerk, Recorder, Registrar of Voters, Clerk-Recorder, Clerk-Recorder-Assessor, as well as their divisions and departments.

Collection contains records of the Sonoma County Water Agency relating to water use and management of the Agency's properties throughout Sonoma County. Includes formal documents placing a valuation on property owned by the Agency and various reports on the amount of water pumped by the agency and stored or delivered to customers. Includes the Russian River and Sonoma Valley sanitation districts, both managed by the Water Agency.