 The population density was 1,628 people per square mile (628/km²).There were 255,154 housing units at an average density of 639 per square mile (247/km²).The racial makeup of the county was 89.02% White or European American, 3.18% Black or 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.