As of the census of 2000, there were 152,538 people, 59,894 households, and 39,050 families residing in the county. The population density was 233 people per square mile (90/km²). There were 66,120 housing units at an average density of 101 per square mile (39/km²). The racial makeup of the county was 91.13% White, 4.69% Black or African American, 0.23% Native American, 1.71% Asian, 0.02% Pacific Islander, 0.89% from other races, and 1.34% from two or more races. 2.11% of the population were Hispanic or Latino of any race. 22.3% were of Irish, 14.7% Italian, 12.8% German, 7.5% English, 6.2% French and 5.3% American ancestry according to Census 2000. 93.4% spoke English and 2.0% Spanish as their first language.
There were 59,894 households out of which 31.30% had children under the age of 18 living with them, 48.80% were married couples living together, 12.00% had a female householder with no husband present, and 34.80% were non-families. 27.90% of all households were made up of individuals and 10.30% had someone living alone who was 65 years of age or older. The average household size was 2.46 and the average family size was 3.02.
In the county the population was spread out with 24.20% under the age of 18, 10.10% from 18 to 24, 29.10% from 25 to 44, 23.00% from 45 to 64, and 13.60% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 95.90 males. For every 100 females age 18 and over, there were 93.70 males.
The median income for a household in the county was $42,905, and the median income for a family was $52,864. Males had a median income of $36,666 versus $28,153 for females. The per capita income for the county was $21,095. About 6.70% of families and 9.50% of the population were below the poverty line, including 11.90% of those under age 18 and 6.60% of those age 65 or over.