Sussex County is Delaware's largest county by land area, with 938 square miles (2,429 km). The first European settlement in the state of Delaware was founded in 1631 near the present-day town of Lewes. However, Sussex County was not organized until 1683.
As of the census of 2000, there were 156,638 people, 62,577 households, and 43,866 families residing in the county. The population density was 167 people per square mile (64/km²). There were 93,070 housing units at an average density of 99 per square mile (38/km²). The racial makeup of the county was 80.35% White, 14.89% Black or African American, 0.60% Native American, 0.75% Asian, 0.04% Pacific Islander, 2.02% from other races, and 1.35% from two or more races. 4.41% of the population were Hispanic or Latino of any race. 14.9% were of English, 14.3% United States or American, 12.9% Irish, 12.5% German and 5.6% Italian ancestry according to Census 2000. 93.3% spoke English and 4.3% Spanish as their first language.
There were 62,577 households out of which 27.10% had children under the age of 18 living with them, 54.90% were married couples living together, 11.30% had a female householder with no husband present, and 29.90% were non-families. 24.30% of all households were made up of individuals and 11.10% had someone living alone who was 65 years of age or older. The average household size was 2.45 and the average family size was 2.88.
In the county the population was spread out with 22.50% under the age of 18, 7.00% from 18 to 24, 26.30% from 25 to 44, 25.60% from 45 to 64, and 18.50% who were 65 years of age or older. The median age was 41 years. For every 100 females there were 95.50 males. For every 100 females age 18 and over, there were 92.80 males.
The median income for a household in the county was $39,208, and the median income for a family was $45,203. Males had a median income of $30,811 versus $23,625 for females. The per capita income for the county was $20,328. About 7.70% of families and 10.50% of the population were below the poverty line, including 15.00% of those under age 18 and 8.40% of those age 65 or over.