Washington County is one of 36 counties in the U.S. state of Oregon. As of the 2010 United States Census, the population was 529,710, making it the state’s second most populous county. The county seat and largest city is Hillsboro.
According to the US Census Bureau, the county has a total area of 726 square miles (1,880 km), of which 724 square miles (1,880 km) is land and 2.2 square miles (5.7 km) (0.3%) is water. It is located approximately 20 miles (32 km) to the west of Portland. The Portland Metro Urban Growth Boundary (UGB) bisects the county. The county’s highest point is South Saddle Mountain at 3,464 feet (1,056 m) above sea level in the Northern Oregon Coast Range.
Most of the county is in the Tualatin Valley, formed by the Tualatin Mountains to the east and north, the Chehalem Mountains to the south, and the Northern Oregon Coast Range to the west and north. The county’s only river is the Tualatin River, flowing through the Tualatin Plains. The northern and western portions of the county are forested, while the remainder of the county includes urban areas, agricultural lands, and floodplains.
As of the 2000 United States Census, there were 445,342 people, 169,162 households, and 114,015 families in the county. The population density was 615/sqmi (238/km²). There were 178,913 housing units at an average density of 247/sqmi (95/km²). The racial makeup of the county was 82.19% White, 1.15% Black or African American, 0.65% Native American, 6.68% Asian, 0.30% Pacific Islander, 5.86% from other races, and 3.17% from two or more races. 11.17% of the population were Hispanic or Latino of any race. 17.2% were of German, 9.9% English, 8.2% Irish, and 6.7% American ancestry. 81.7% spoke only English at home, while 9.6% spoke Spanish and 1.2% Vietnamese.
There were 169,162 households out of which 35.60% had children under the age of 18 living with them, 54.50% were married couples living together, 9.00% had a female householder with no husband present, and 32.60% were non-families. 24.70% of all households were made up of individuals and 6.70% had someone living alone who was 65 years of age or older. The average household size was 2.61 and the average family size was 3.14.
The county population contained 26.90% under the age of 18, 9.30% from 18 to 24, 34.10% from 25 to 44, 20.90% from 45 to 64, and 8.80% who were 65 years of age or older. The median age was 33 years. For every 100 females, there were 99.10 males. For every 100 females age 18 and over, there were 97.00 males.
The median income for a household in the county was $52,122, and the median income for a family was $61,499. Males had a median income of $43,304 versus $31,074 for females. The per capita income for the county was $24,969. About 4.90% of families and 7.40% of the population were below the poverty line, including 8.30% of those under age 18 and 5.30% of those age 65 or over.
As of the 2010 United States Census, there were 529,710 people, 200,934 households, and 134,323 families residing in the county. The population density was 731.4 inhabitants per square mile (282.4/km). There were 212,450 housing units at an average density of 293.3 per square mile (113.2/km). The racial makeup of the county was 76.6% white, 8.6% Asian, 1.8% black or African American, 0.7% American Indian, 0.5% Pacific islander, 7.5% from other races, and 4.3% from two or more races. Those of Hispanic or Latino origin made up 15.7% of the population. In terms of ancestry, 20.8% were German, 12.4% were English, 12.1% were Irish, and 3.2% were American.
Of the 200,934 households, 36.0% had children under the age of 18 living with them, 52.2% were married couples living together, 10.1% had a female householder with no husband present, 33.2% were non-families, and 25.1% of all households were made up of individuals. The average household size was 2.60 and the average family size was 3.14. The median age was 35.3 years.
The median income for a household in the county was $62,574 and the median income for a family was $76,778. Males had a median income of $54,417 versus $40,254 for females. The per capita income for the county was $30,522. About 6.7% of families and 9.5% of the population were below the poverty line, including 12.5% of those under age 18 and 6.7% of those age 65 or over.