Somerset County is the seventh-wealthiest county in the United States by per capita income and the highest in New Jersey. Somerset County has the tenth-highest personal per capita income of any U.S. county and the second-highest in New Jersey. The county also ranks sixth in the United States in terms of median income.
Somerset County was created on May 14, 1688, from portions of Middlesex County.
As of the census of 2000, there were 297,490 people, 108,984 households, and 78,359 families residing in the county. The population density was 976 people per square mile (377/km²). There were 112,023 housing units at an average density of 368 per square mile (142/km²). The racial makeup of the county was 79.34% White, 7.53% Black or African American, 0.13% Native American, 8.38% Asian, 0.04% Pacific Islander, 2.74% from other races, and 1.83% from two or more races. 8.68% of the population were Hispanic or Latino of any race. 17.6% were of Italian, 11.4% Irish, 9.3% German and 7.5% Polish ancestry according to Census 2000.
There were 108,984 households out of which 36.20% had children under the age of 18 living with them, 60.60% were married couples living together, 8.20% had a female householder with no husband present, and 28.10% were non-families. 22.80% of all households were made up of individuals and 7.00% had someone living alone who was 65 years of age or older. The average household size was 2.69 and the average family size was 3.19.
In the county the population was spread out with 25.50% under the age of 18, 5.90% from 18 to 24, 33.80% from 25 to 44, 23.50% from 45 to 64, and 11.20% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 95.40 males. For every 100 females age 18 and over, there were 92.10 males.
The median income for a household in the county was $76,933 and the median income for a family was $90,605 (these figures had risen to $94,036 and $109,488 respectively as of a 2007 estimate). Males had a median income of $60,602 versus $41,824 for females. The per capita income for the county was $37,970. The poverty rate is 1.7%, the lowest of any county in the United States with 250,000 or more people. Out of the total population, 3.80% of those under the age of 18 and 4.90% of those 65 and older were living below the poverty line.