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.