Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Solano County is a county located in Bay-Delta region of the U.S. state of California, about halfway between San Francisco and Sacramento and is one of the nine San Francisco Bay Area counties. As of 2000 its population was 394,542. The county seat is Fairfield and the largest city is Vallejo.Solano County was one of the original counties of California, created in 1850 at the time of statehood. Prior to statehood, it had been referred to as Benicia County.