Santa Rosa is the county seat

County seat

A county seat is an administrative center, or seat of government, for a county or civil parish. The term is primarily used in the United States....

 of Sonoma County

Sonoma County, California

Sonoma County, located on the northern coast of the U.S. state of California, is the largest and northernmost of the nine San Francisco Bay Area counties. Its population at the 2010 census was 483,878. Its largest city and county seat is Santa Rosa....

, California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, United States. The 2010 census reported a population of 167,815. Santa Rosa is the largest city in California's Wine Country and fifth largest city in the San Francisco Bay Area

San Francisco Bay Area

The San Francisco Bay Area, commonly known as the Bay Area, is a populated region that surrounds the San Francisco and San Pablo estuaries in Northern California. The region encompasses metropolitan areas of San Francisco, Oakland, and San Jose, along with smaller urban and rural areas...

, after San Jose

San Jose, California

San Jose is the third-largest city in California, the tenth-largest in the U.S., and the county seat of Santa Clara County which is located at the southern end of San Francisco Bay...

, San Francisco

San Francisco, California

San Francisco , officially the City and County of San Francisco, is the financial, cultural, and transportation center of the San Francisco Bay Area, a region of 7.15 million people which includes San Jose and Oakland...

, Oakland

Oakland, California

Oakland is a major West Coast port city on San Francisco Bay in the U.S. state of California. It is the eighth-largest city in the state with a 2010 population of 390,724...

, and Fremont

Fremont, California

Fremont is a city in Alameda County, California. It was incorporated on January 23, 1956, from the merger of five smaller communities: Centerville, Niles, Irvington, Mission San Jose, and Warm Springs...

 and 26th largest city in California.
The first known permanent European settlement of Santa Rosa was the homestead of the Carrillo family, in-laws to Mariano Guadalupe Vallejo

Mariano Guadalupe Vallejo

Mariano Guadalupe Vallejo was a Californian military commander, politician, and rancher. He was born a subject of Spain, performed his military duties as an officer of Mexico, and shaped the transition of California from a Mexican district to an American state...

, who settled the Sonoma

Sonoma, California

Sonoma is a historically significant city in Sonoma Valley, Sonoma County, California, USA, surrounding its historic town plaza, a remnant of the town's Mexican colonial past. It was the capital of the short-lived California Republic...

 pueblo

Pueblo

Pueblo is a term used to describe modern communities of Native Americans in the Southwestern United States of America. The first Spanish explorers of the Southwest used this term to describe the communities housed in apartment-like structures built of stone, adobe mud, and other local material...

 and Petaluma

Petaluma, California

Petaluma is a city in Sonoma County, California, in the United States. In the 2010 Census the population was 57,941.Located in Petaluma is the Rancho Petaluma Adobe, a National Historic Landmark. It was built beginning in 1836 by General Mariano Guadalupe Vallejo, then Commandant of the San...

 area.