Sonoma County is a county in the U.S. state of California. As of the 2010 United States Census, its population was 483,878. Its county seat and largest city is Santa Rosa. It is located to the north of Marin County and the south of Mendocino County. It is west of Napa County and Lake County. Sonoma County comprises the Santa Rosa, CA Metropolitan Statistical Area, which is also included in the San Jose-San Francisco-Oakland, CA Combined Statistical Area. It is the northwestern county in the nine-county San Francisco Bay Area region. Sonoma is the southwestern county and largest producer of Californias Wine Country region, which also includes Napa, Mendocino, and Lake counties. It has 13 approved American Viticultural Areas and over 250 wineries. In 2002, Sonoma County ranked as the 32nd county in the United States in agricultural production. As early as 1920, Sonoma County was ranked as the eighth most agriculturally productive US county and a leading producer of hops, grapes, prunes, apples, and dairy and poultry products, largely due to the extent of available, fertile agricultural land in addition to the abundance of high quality irrigation water. More than 7.4 million tourists visit each year, spending more than $1 billion in 2006. Sonoma County is the home of Sonoma State University and Santa Rosa Junior College.