As of the census of 2000, there were 149,577 people, 56,057 households, and 38,455 families residing in the county. The population density was 548 people per square mile (212/km²). There were 59,989 housing units at an average density of 220 per square mile (85/km²). The racial makeup of the county was 88.38% White, 5.08% Black or African American, 0.38% Native American, 0.92% Asian, 0.04% Pacific Islander, 3.29% from other races, and 1.91% from two or more races. 7.19% of the population were Hispanic or Latino of any race. 28.8% were of German, 10.4% Italian, 7.9% Irish and 7.6% Polish ancestry according to Census 2000.
There were 56,057 households out of which 34.80% had children under the age of 18 living with them, 52.70% were married couples living together, 11.50% had a female householder with no husband present, and 31.40% were non-families. 25.50% of all households were made up of individuals and 9.10% had someone living alone who was 65 years of age or older. The average household size was 2.60 and the average family size was 3.13.
In the county, the population was spread out with 27.10% under the age of 18, 9.40% from 18 to 24, 31.30% from 25 to 44, 20.70% from 45 to 64, and 11.50% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 98.30 males. For every 100 females age 18 and over, there were 95.30 males.