

Sonoma
County is available for adoption.
If you have a local connection to Sonoma County or
an interest in California in general,
Please consider joining the CAGenWeb as a County
Coordinator.
Contact Bob
Jenkins if you are interested.
In addition:, we would appreciate any
contribution that you would like to make to this
site: biographies, obituaries, birth,
marriage, death info, grave info,
photographs....etc
Sonoma
County, California
Spanish exploration reached the area in the late 1700s, culminating in the establishment of Mission San Francisco Solano in 1823 at Sonoma—the last and northernmost mission in Alta California. After Mexican independence, the region transitioned into a landscape of ranchos, including the extensive holdings of General Mariano Guadalupe Vallejo, whose influence anchored early civic and military life.
Sonoma County entered a new era after the 1846 Bear Flag Revolt, when American settlers declared the short‑lived California Republic in the town of Sonoma. Following U.S. annexation and the Gold Rush, the county grew rapidly as migrants arrived to farm, raise livestock, mill lumber, and establish small towns throughout the valleys and along the Russian River.
When Sonoma County was organized in 1850,
the town of Sonoma was selected as the first county
seat, reflecting its prominence during the mission
and rancho eras. As settlement expanded northward, the seat
was moved to Santa Rosa in 1854, where it
remains today.
The arrival of the railroad in the 1870s connected Sonoma’s agricultural communities to wider markets, supporting dairy farms, orchards, and the early wine industry. By the early 20th century, viticulture, coastal fishing, and tourism helped define the county’s identity.
Today, Sonoma County includes communities such as Santa Rosa, Petaluma, Sonoma, Healdsburg, Sebastopol, and Cloverdale. For genealogists, its records reflect layers of Native heritage, mission and rancho‑era documents, pioneer settlement, agricultural development, and the growth of one of California’s most historic wine‑producing regions.