Stanislaus County is included in the Modesto Metropolitan Statistical Area.
As of the census of 2000, there were 446,997 people, 145,146 households, and 109,585 families residing in the county. The population density was 299 people per square mile (116/km²). There were 150,807 housing units at an average density of 101 per square mile (39/km²). The racial/ethnic makeup of the county was 69.33% White, 2.58% Black, 4.22% Asian, 1.27% Native American, 0.34% Pacific Islander, 16.82% from other races, and 5.44% from two or more races. 31.74% of the population were Hispanic or Latino of any race. 8.4% were of German, 6.3% English, 6.0% American, 5.5% Irish, and 5.1% Portuguese ancestry according to Census 2000. 67.8% spoke English, 23.7% Spanish, 1.5% Syriac, and 1.3% Portuguese as their first language.
There were 145,146 households out of which 41.20% had children under the age of 18 living with them, 56.0% were married couples living together, 13.7% had a female householder with no husband present, and 24.5% were non-families. 19.4% of all households were made up of individuals and 7.9% had someone living alone who was 65 years of age or older. The average household size was 3.03 and the average family size was 3.47.
In the county the population was spread out with 31.1% under the age of 18, 9.8% from 18 to 24, 29.0% from 25 to 44, 19.5% from 45 to 64, and 10.4% who were 65 years of age or older. The median age was 32 years. For every 100 females there were 96.8 males. For every 100 females age 18 and over, there were 93.4 males.
The median income for a household in the county was $40,101, and the median income for a family was $44,703. Males had a median income of $36,969 versus $26,595 for females. The per capita income for the county was $16,913. About 12.3% of families and 16.0% of the population were below the poverty line, including 20.5% of those under age 18 and 8.8% of those age 65 or over.
Modesto City-County Airport has a number of scheduled passenger flights. Other (general aviation) airports around the county include Oakdale Airport, Patterson Airport, and Turlock Airpark.