According to the U.S. Census Bureau, the county has a total area of 1,363 km² (526 mi²). 1,301 km² (502 mi²) of it is land and 62 km² (24 mi²) of it is water. The total area is 4.53% water.
As of the census2 of 2000, there are 569,891 people, 237,405 households, and 138,169 families residing in the county. The population density is 438/km² (1,135/mi²). There are 252,977 housing units at an average density of 194/km² (504/mi²). The racial makeup of the county is 66.99% White, 25.92% Black or African American, 0.29% Native American, 2.33% Asian, 0.07% Pacific Islander, 2.42% from other races, and 1.97% from two or more races. 4.58% of the population are Hispanic or Latino of any race.
There are 237,405 households out of which 26.70% have children under the age of 18 living with them, 39.90% are married couples living together, 14.30% have a female householder with no husband present, and 41.80% are non-families. 33.40% of all households are made up of individuals and 8.20% have someone living alone who is 65 years of age or older. The average household size is 2.30 and the average family size is 2.96.
In the county, the population is spread out with 22.20% under the age of 18, 11.60% from 18 to 24, 34.00% from 25 to 44, 21.10% from 45 to 64, and 11.10% who are 65 years of age or older. The median age is 34 years. For every 100 females there are 93.80 males. For every 100 females age 18 and over, there are 90.80 males.
The median income for a household in the county is $39,797, and the median income for a family is $49,317. Males have a median income of $33,844 versus $27,770 for females. The per capita income for the county is $23,069. 13.00% of the population and 10.00% of families are below the poverty line. Out of the total people living in poverty, 19.10% are under the age of 18 and 10.50% are 65 or older.