Sonoma County, CA Genweb Project a collection of online resources for genealogy researchers
Sonoma County - American Local History Network has several pages of information for this county
Sonoma County, CA Genealogy Forum read and post messages about your ancestors for this county
Sonoma County Message Board read and post messages with other genealogy researchers of this county
Sonoma Co. 1850 Census
The Tombstone Transcription Project - cemeteries for Sonoma Co. CA
US GenWeb Archives for Sonoma County cemeteries, newspapers, wills, military rosters etc recorded online
Western Sonoma County Historical Society
1906 Earthquake - List of Dead

Additional Resources

California Newspaper Search enter your California ancestor's name to instantly search the world's largest newspaper archive; over 12 million newspaper pages
California Birth Records
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California Death Records