Geography According to the U.S. Census Bureau, the county has a total area of 1,150 km² (444 mi²). 1,035 km² (400 mi²) of it is land and 115 km² (44 mi²) of it is water. The total area is 9.99% water.
Demographics As of the census of 2000, there are 650,308 people, 248,827 households, and 165,967 families residing in the county. The population density is 628/km² (1,628/mi²). There are 255,154 housing units at an average density of 247/km² (639/mi²). The racial makeup of the county is 89.02% White, 3.18% African American, 0.13% Native American, 5.50% Asian, 0.02% Pacific Islander, 0.78% from other races, and 1.37% from two or more races. 1.84% of the population are Hispanic or Latino of any race.
There are 248,827 households out of which 31.20% have children under the age of 18 living with them, 54.20% are married couples living together, 9.50% have a female householder with no husband present, and 33.30% are non-families. 26.80% of all households are made up of individuals and 10.80% have someone living alone who is 65 years of age or older. The average household size is 2.54 and the average family size is 3.14.
In the county the population is spread out with 23.40% under the age of 18, 7.00% from 18 to 24, 31.60% from 25 to 44, 23.50% from 45 to 64, and 14.40% who are 65 years of age or older. The median age is 38 years. For every 100 females there are 91.40 males. For every 100 females age 18 and over, there are 87.60 males.
The median income for a household in the county is $63,432, and the median income for a family is $77,847. Males have a median income of $51,301 versus $37,108 for females. The per capita income for the county is $32,484. 4.60% of the population and 2.90% of families are below the poverty line. Out of the total people living in poverty, 4.40% are under the age of 18 and 5.70% are 65 or older.