As of the 2010 Census, there were 541,781 people, 222,781 households, and 141,110 families residing in the county. The population density was . There were 245,109 housing units at an average density of . The racial makeup of the county was 80.6% white, 14.4% black or African American, 2.2% Asian, 0.2% American Indian, 0.5% from other races, and 2.1% from two or more races. Those of Hispanic or Latino origin made up 1.6% of the population. In terms of ancestry, 24.9% were German, 15.3% were Irish, 10.6% were English, 10.1% were Italian, 5.1% were Polish, and 4.5% were American.