According to the U.S. Census Bureau, the county has a total area of 3,543 km² (1,368 mi²). 1,159 km² (448 mi²) of it is land and 2,384 km² (920 mi²) of it is water. The total area is 67.28% water.
As of the census2 of 2000, there are 644,356 people, 216,297 households, and 163,953 families residing in the county. The population density is 556/km² (1,440/mi²). There are 225,919 housing units at an average density of 195/km² (505/mi²). The racial makeup of the county is 80.11% White, 6.94% Black or African American, 0.28% Native American, 3.90% Asian, 0.05% Pacific Islander, 6.72% from other races, and 2.01% from two or more races. 14.39% of the population are Hispanic or Latino of any race.
There are 216,297 households out of which 42.10% have children under the age of 18 living with them, 63.20% are married couples living together, 9.20% have a female householder with no husband present, and 24.20% are non-families. 19.70% of all households are made up of individuals and 6.20% have someone living alone who is 65 years of age or older. The average household size is 2.88 and the average family size is 3.33.
In the county the population is spread out with 29.40% under the age of 18, 8.90% from 18 to 24, 31.60% from 25 to 44, 21.60% from 45 to 64, and 8.50% who are 65 years of age or older. The median age is 34 years. For every 100 females there are 101.20 males. For every 100 females age 18 and over, there are 99.30 males.
The median income for a household in the county is $66,973, and the median income for a family is $76,424. Males have a median income of $50,789 versus $33,458 for females. The per capita income for the county is $32,102. 5.70% of the population and 4.00% of families are below the poverty line. Out of the total people living in poverty, 7.00% are under the age of 18 and 4.80% are 65 or older.
Cities and towns