Chester County is one of the three original counties of Pennsylvania created by William Penn in 1682. It is named for Cheshire, England. It is part of the Delaware Valley area, and is the only Delaware Valley county in Pennsylvania that does not border Philadelphia, though it is close.
As of the census of 2000, there were 433,501 people, 157,905 households, and 113,375 families residing in the county. The population density was 573 people per square mile (221/km²). There were 163,773 housing units at an average density of 217 per square mile (84/km²). The racial makeup of the county was 89.21% White, 6.24% Black or African American, 0.15% Native American, 1.95% Asian, 0.03% Pacific Islander, 1.35% from other races, and 1.06% from two or more races. 3.72% of the population were Hispanic or Latino of any race. 18.0% were of Irish, 17.3% German, 13.1% Italian, 10.1% English and 5.6% American ancestry according to Census 2000. 91.4% spoke English and 3.7% Spanish as their first language.
There were 157,905 households out of which 35.10% had children under the age of 18 living with them, 60.50% were married couples living together, 8.10% had a female householder with no husband present, and 28.20% were non-families. 22.60% of all households were made up of individuals and 7.60% had someone living alone who was 65 years of age or older. The average household size was 2.65 and the average family size was 3.15.
In the county, the population was spread out with 26.20% under the age of 18, 7.90% from 18 to 24, 30.40% from 25 to 44, 23.80% from 45 to 64, and 11.70% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 96.40 males. For every 100 females age 18 and over, there were 93.10 males.
The median income for a household in the county was $65,295, and the median income for a family was $76,916 (these figures had risen to $80,818 and $97,894 respectively as of a 2007 estimate). Males had a median income of $51,223 versus $34,854 for females. The per capita income for the county was $31,627. About 3.10% of families and 5.20% of the population were below the poverty line, including 5.10% of those under age 18 and 5.50% of those age 65 or over.
The region was originally occupied by the Lenni Lenape people who greeted European settlers in the seventeenth century with amity and kindness. British settlers were mostly English, Scotch-Irish and Welsh in ethnicity. As time passed, the region has had large influxes of Germans, Africans, Eastern Europeans, Italians, Puerto Ricans, and Mexicans.