According to the U.S. Census Bureau, the county has a total area of 3,923 km² (1,515 mi²). 3,869 km² (1,494 mi²) of it is land and 54 km² (21 mi²) of it is water. The total area is 1.38% water.
As of the census2 of 2000, there are 446,997 people, 145,146 households, and 109,585 families residing in the county. The population density is 116/km² (299/mi²). There are 150,807 housing units at an average density of 39/km² (101/mi²). The racial makeup of the county is 69.33% White, 2.58% Black or African American, 1.27% Native American, 4.22% Asian, 0.34% Pacific Islander, 16.82% from other races, and 5.44% from two or more races. 31.74% of the population are Hispanic or Latino of any race.
There are 145,146 households out of which 41.20% have children under the age of 18 living with them, 56.00% are married couples living together, 13.70% have a female householder with no husband present, and 24.50% are non-families. 19.40% of all households are made up of individuals and 7.90% have someone living alone who is 65 years of age or older. The average household size is 3.03 and the average family size is 3.47.
In the county the population is spread out with 31.10% under the age of 18, 9.80% from 18 to 24, 29.00% from 25 to 44, 19.50% from 45 to 64, and 10.40% who are 65 years of age or older. The median age is 32 years. For every 100 females there are 96.80 males. For every 100 females age 18 and over, there are 93.40 males.
The median income for a household in the county is $40,101, and the median income for a family is $44,703. Males have a median income of $36,969 versus $26,595 for females. The per capita income for the county is $16,913. 16.00% of the population and 12.30% of families are below the poverty line. Out of the total people living in poverty, 20.50% are under the age of 18 and 8.80% are 65 or older.