As of the 2010 United States Census, there were 529,710 people, 200,934 households, and 134,323 families residing in the county. The population density was . There were 212,450 housing units at an average density of . The racial makeup of the county was 76.6% white, 8.6% Asian, 1.8% black or African American, 0.7% American Indian, 0.5% Pacific islander, 7.5% from other races, and 4.3% from two or more races. Those of Hispanic or Latino origin made up 15.7% of the population. In terms of ancestry, 20.8% were German American, 12.4% were English American, 12.1% were Irish American, and 3.2% were Americans.. What was the most prevalent ethnicity?