Outdoor Advertising Billboards for Rent in Washington County, Oregon

Washington County is one of 36 counties in the U.S. state of Oregon. Originally named Twality when created in 1843, the territorial legislature renamed it for the first president of the United States, George Washington, in 1849. The original boundaries included the entire northwest corner of Oregon before sections became new counties. Washington County contains only one river, the Tualatin River, and its drainage basin is almost entirely within the county. The county is nearly conterminous with the Tualatin Valley and is bordered on the west and north by the Northern Oregon Coast Range, on the south by the Chehalem Mountains, and on the north and east by the Tualatin Mountains (or West Hills).

In 2000 census, its population was 445,342. As of 2008, the estimate is 519,925, making it the second most populous county in the state. The seat and largest city is Hillsboro. Other cities include Beaverton, Tigard, and Forest Grove, the oldest city in the county. Major roads in the county include small sections of Interstate 5 and Interstate 205, the Sunset Highway, Oregon Route 217, Oregon Route 47, Oregon Route 10, and Oregon Route 8. Public transportation is primarily operated by TriMet and includes buses, the Westside Express Service commuter rail, and MAX Light Rail. Other transportation includes air travel at the Hillsboro Airport, several private airfields and heliports, and heavy rail cargo on several rail lines.

Demographics

Historical populations
Census	Pop.		%±
1900	14,467		—
1910	21,522		48.8%
1920	26,376		22.6%
1930	30,275		14.8%
1940	39,194		29.5%
1950	61,269		56.3%
1960	92,237		50.5%
1970	157,920		71.2%
1980	245,808		55.7%
1990	311,554		26.7%
2000	445,342		42.9%
Est. 2007	522,514		17.3%
sources:

As of the census of 2000, there were 445,342 people, 169,162 households, and 114,015 families residing in the county. The population density was 615 people per square mile (238/km²). There were 178,913 housing units at an average density of 247 per square mile (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 according to Census 2000. 81.7% spoke English, 9.6% Spanish and 1.2% Vietnamese as their first language.

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.

In the county, the population was spread out with 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.