San Joaquin County is one of California's original counties, created when California became a state in 1850. It's named for the 356-mile-long San Joaquin River, the longest river in California's Central Valley. The river passes through San Joaquin County and empties into the Sacramento-San Joaquin River Delta, the largest estuary on the west coast of the Americas (North, Central, and South).

Incorporated cities currently within San Joaquin County are Escalon, Lathrop, Lodi, Manteca, Mountain House, Ripon, Stockton, and Tracy; unincorporated  communities are Acampo, Clements, Collegeville, Farmington, French Camp,  Linden, Lockeford, Morada, Terminous, Thornton, Victor, Waterloo, and Woodbridge. Stockton is the county seat for San Joaquin County. A brief history of Stockton can be found on the Visit Stockton website

Historic settlements and communities that no longer exist include Atlanta, Banta, Bellota, Burwood, Carnegie, Castoria, China Flat, Collierville, Cox's Ferry, Dent (now Escalon), Dogtown, Elliott, Fair Oaks, Five Corners, Henderson Village, Holt, Hope Landing, Liberty, Lincoln Village (now within Stockton), Middle River, Mokelumne City, Mormon, Peters, Poland, San Joaquin, New Jerusalem, Peters, Taison, Vernalis, and Youngstown. 

For a highly detailed 1895 map of San Joaquin County showing communities and property ownership, click on this link to the Library of Congress. From this site, you can download map images with different resolutions. For current and archival maps of San Joaquin County, visit the San Joaquin County Geographic Information Systems website.

There are 11 townships in San Joaquin County: Castoria, Dent, Douglass, Elkhorn, Elliott, Liberty, O'Neal, Ripon, Stockton, Tulare, and Union. See the San Joaquin County ordinance code for legal descriptions of each township.

Historic San Joaquin County Seal, 1888-1962