As of the census of 2000, there were 563,598 people, 181,629 households, and 134,768 families residing in the county. The population density was 403 people per square mile (156/km²). There were 189,160 housing units at an average density of 135 per square mile (52/km²). The racial makeup of the county was 58.13% White, 6.69% Black or African American, 1.13% Native American, 11.41% Asian, 0.35% Pacific Islander, 16.26% from other races, and 6.05% from two or more races. 30.53% of the population were Hispanic or Latino of any race. 9.3% were of German, 5.3% Irish and 5.0% English ancestry according to Census 2000. 66.4% spoke English, 21.3% Spanish, 2.2% Tagalog, 1.8% Mon-Khmer or Cambodian, 1.1% Vietnamese and 1.1% Hmong as their first language.
There were 181,629 households out of which 40.5% had children under the age of 18 living with them, 54.3% were married couples living together, 14.0% had a female householder with no husband present, and 25.8% were non-families. 20.7% of all households were made up of individuals and 8.4% had someone living alone who was 65 years of age or older. The average household size was 3.00 and the average family size was 3.48.
In the county the population was spread out with 31.0% under the age of 18, 10.0% from 18 to 24, 28.8% from 25 to 44, 19.6% from 45 to 64, and 10.6% who were 65 years of age or older. The median age was 32 years. For every 100 females there were 99.9 males. For every 100 females age 18 and over, there were 97.2 males.
The median income for a household in the county was $41,282, and the median income for a family was $46,919. Males had a median income of $39,246 versus $27,507 for females. The per capita income for the county was $17,365. About 13.5% of families and 17.7% of the population were below the poverty line, including 23.7% of those under age 18 and 10.0% of those age 65 or over.
San Joaquin Regional Transit District provides city bus service within Stockton. RTD also runs intercity routes throughout the county, and subscription commuter routes to Livermore, Pleasanton, Sacramento and Santa Clara County.
The cities of Lodi, Manteca, Tracy and Ripon operate their own bus systems.
Greyhound buses and Amtrak trains both stop in Stockton. Amtrak's San Joaquins Oakland-Bakersfield train stops at the San Joaquin Street Station. Amtrak's San Joaquins Sacramento-Bakersfield trains stop at the Robert J. Cabral Station which is also used by Altamont Commuter Express trains which originate in Stockton.
Stockton Metropolitan Airport features passenger service to Las Vegas and Phoenix, along with cargo service and general aviation. Other general aviation airports in the county include Escalon Airport, Lodi Airport and Tracy Municipal Airport.