As of the census of 2000, there were 793,633 people, 283,736 households, and 193,507 families residing in the county. The population density was 6,285 people per square mile (2,427/km²). There were 301,011 housing units at an average density of 2,384 per square mile (920/km²). The racial makeup of the county was 44.46% White, 41.24% Black or African American, 0.23% Native American, 3.71% Asian, 0.05% Pacific Islander, 6.88% from other races, and 3.42% from two or more races. 15.42% of the population were Hispanic or Latino of any race. 12.3% were of Italian, 5.7% West Indian and 5.6% Irish ancestry according to Census 2000.
There were 283,736 households out of which 33.80% had children under the age of 18 living with them, 42.30% were married couples living together, 20.40% had a female householder with no husband present, and 31.80% were non-families. 26.70% of all households were made up of individuals and 9.60% had someone living alone who was 65 years of age or older. The average household size was 2.72 and the average family size was 3.30.
In the county the population was spread out with 26.10% under the age of 18, 9.40% from 18 to 24, 31.10% from 25 to 44, 21.50% from 45 to 64, and 11.90% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 90.70 males. For every 100 females age 18 and over, there were 86.40 males.
The median income for a household in the county was $44,944, and the median income for a family was $54,818. Males had a median income of $41,374 versus $32,052 for females. The per capita income for the county was $24,943. About 12.80% of families and 15.60% of the population were below the poverty line, including 20.50% of those under age 18 and 12.20% of those age 65 or over.
The county has a high Italian population, with significant percentages of residents (over 25%) in several communities, of the West Essex area and northeastern district, mostly in the northern half of the county, being of Italian descent. This includes the communities of Belleville (30.9%), Bloomfield (26.4%), Caldwell (26.3%), Cedar Grove (34.8%), Fairfield (45.8%), Nutley (44.5%), Roseland (38.7%), Verona (34.3%) and West Caldwell (35.2%).
The county has a notable Jewish population, with 76,200 Jewish residents according to the 2002 results of the National Jewish Population Survey.
As of 2005 36.4% of the population was non-Hispanic whites. African Americans made up 42.6% of the population. Latinos formed 17.5% of the population. 4.2% of the population was Asian, as the municipalities of Belleville, Bloomfield, West Orange, Livingston, Millburn, Nutley, and Cedar Grove have Asian populations of 5% or more.