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Washington County, Oregon facts for kids

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Washington County
Washington County Courthouse entrance sign.JPG
Meier Road Barn (Washington County, Oregon scenic images) (washDA0034).jpg
Canola Field in Flower (Washington County, Oregon scenic images) (washDA0035).jpg
From top, left to right: Washington County courthouse, Meier Road Barn, a canola field in rural Washington County
Official seal of Washington County
Map of Oregon highlighting Washington County
Location within the U.S. state of Oregon
Map of the United States highlighting Oregon
Oregon's location within the U.S.
Country  United States
State  Oregon
Founded July 5, 1843 (as Twality District)
Named for George Washington
Seat Hillsboro
Largest city Hillsboro
 • Total 726 sq mi (1,880 km2)
 • Land 724 sq mi (1,880 km2)
 • Water 2.2 sq mi (6 km2)  0.3%%
 • Total 600,372
 • Estimate 
600,811 Increase
 • Density 826/sq mi (319/km2)
Time zone UTC−8 (Pacific)
 • Summer (DST) UTC−7 (PDT)
Congressional district 1st

Washington County is one of 36 counties in the U.S. state of Oregon and part of the Portland metropolitan area. The 2020 census recorded the population as 600,372, making it the second most populous county in the state and most populous "Washington County" in the United States. Hillsboro is the county seat and largest city, while other major cities include Beaverton, Tigard, Cornelius, Banks, Gaston, Sherwood, North Plains, and Forest Grove, the county's oldest city.

Originally named Twality when created in 1843, the Oregon Territorial Legislature renamed it for the nation's first president in 1849 and included the entire northwest corner of Oregon before new counties were created in 1854. The Tualatin River and its drainage basin lie almost entirely within the county, which shares its boundaries with the Tualatin Valley. It 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.

Major roads include sections of Interstate 5 and 205, the Sunset Highway, Oregon Route 217, 47, 10, 6 and 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 Hillsboro Airport, private airfields and heliports, and heavy rail cargo on rail lines.


Washington County Jail - Hillsboro, Oregon
Current county jail in Hillsboro.

The Provisional Legislature of Oregon created the county as Twality District on July 5, 1843. Twality was one of the original four districts of the Provisional Government of Oregon in Oregon Country along with Clackamas, Champooick (later Marion), and Yamhill counties. Columbia, later known as Hillsboro, was selected as the county seat in 1850. Washington County obtained its present boundaries in 1854 with the creation of Columbia County to the north and Multnomah County to the east.

The construction of Canyon Road to Beaverton helped Portland to consolidate its position as the primary port of Oregon, and defeat the rival efforts of settlements such as Oregon City and Milwaukie.

In November 2004, the County and the City of Beaverton agreed to a plan where the city would annex both unincorporated residential neighborhoods as well as high-value areas of land. This would result with Cedar Hills, Garden Home, Raleigh Hills, West Slope being incorporated by 2010, and the communities of Aloha, Bethany, and Cedar Mill at some point after that.

Those plans have since been put on hold after Beaverton attempted to forcibly annex Nike, Inc.'s World Headquarters, which would have increased Nike's taxes substantially. Nike successfully lobbied the legislature for a law that would prohibit their annexation for 99 years. Since that decision, annexation plans have been halted, and Washington County started urban planning to provide city-level services to the unincorporated urban areas in the county.

On January 1, 2014, 160 acres (65 ha) of Multnomah County in the Bethany area transferred to Washington County. The area had originally been split off from Washington County when Multnomah County was created, and was transferred back to allow for development of the property.


According to the U.S. Census Bureau, the county has a total area of 726 square miles (1,880 km2), of which 724 square miles (1,880 km2) is land and 2.2 square miles (5.7 km2) (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, which is surrounded 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. In the valley is the only river in the county, the Tualatin River, the Tualatin Plains, and several small hills.


The Tualatin River is the main river in Washington County. Henry Hagg Lake, southwest of Forest Grove, is the largest lake. The Willamette River lies to the east, the Columbia River to the northeast, and the Pacific Ocean to the west of the county.

Adjacent counties

Washington County, Oregon map
Map of Washington County

Major highways

  • I-5.svg Interstate 5 (freeway)
  • I-205.svg Interstate 205 (freeway)
  • US 26.svg U.S. Route 26 (freeway for part)
  • OR 6.svg Oregon Route 6
  • OR 8.svg Oregon Route 8
  • OR 10.svg Oregon Route 10
  • OR 47.svg Oregon Route 47
  • OR 99W.svg Oregon Route 99W
  • OR 210.svg Oregon Route 210
  • OR 217.svg Oregon Route 217 (freeway)
  • OR 219.svg Oregon Route 219

National protected areas


Historical population
Census Pop.
1850 2,652
1860 2,801 5.6%
1870 4,261 52.1%
1880 7,082 66.2%
1890 11,972 69.0%
1900 14,467 20.8%
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%
2010 529,710 18.9%
2020 600,372 13.3%
2021 (est.) 600,811 13.4%
U.S. Decennial Census
1790-1960 1900-1990
1990-2000 2010-2020

2010 census

As of the 2010 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/km2). There were 212,450 housing units at an average density of 293.3 per square mile (113.2/km2). 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.


Downtown Beaverton Oregon
Downtown Beaverton
Forest Grove Oregon Pacific Avenue 1920
Downtown Forest Grove in 1920


City 1990 population 2000 population 2010 population Incorporated Notes
Banks 563 1,286 1,777 1921
Beaverton 53,310 76,129 89,803 1893
Cornelius 6,148 9,652 11,869 1893
Durham 748 1,382 1,351 1966
Forest Grove 13,559 17,708 21,083 1872
Gaston 563 600 637 1914
Hillsboro 37,520 70,187 91,611 1876 County seat
King City 2,060 1,949 3,111 1966
Lake Oswego 30,576 35,278 36,619 1910 Small portion, most in Clackamas County
North Plains 972 1,605 1,947 1963
Portland 437,319 529,121 583,776 1851 Small portion, most in Multnomah County
Rivergrove 294 324 289 1971 Small portion, most in Clackamas County
Sherwood 3,093 11,791 18,194 1893
Tigard 29,344 41,223 48,035 1961
Tualatin 15,013 22,791 26,054 1913 Small portion also in Clackamas County
Wilsonville 7,106 13,991 19,509 1969 Small portion, most in Clackamas County

Census-designated places

Unincorporated communities


Washington County Courthouse east facade 2015 - Hillsboro Oregon

Washington County is centered on a fertile plain that attracted farmers before the first wagon trains. In 1997, orchards covered 8,403 acres (34 km2) of the county's lands and 1,163 acres (4.7 km2) were devoted to vineyards. Agriculture is still a major industry in Washington County, as are lumber, manufacturing, and food processing.

The development of a large electronics industry during the 1980s and 1990s is the dominating factor of the county economy. California-based Intel, Oregon's largest private for-profit employer, has its largest concentration of employees in the county, mainly in Hillsboro. Other technology companies include Electro Scientific Industries, FEI Company, Qorvo, Tektronix, SolarWorld, Planar Systems, and EPSON.

Nike, one of two Fortune 500 corporations based in Oregon, has its headquarters in Washington County. Until it was acquired by IBM, Sequent Computer Systems was headquartered near Nike. Other companies with headquarters in Washington County include optical instruments manufacturer Leupold & Stevens, Columbia Sportswear, and Reser's Fine Foods.

Images for kids

See also

Kids robot.svg In Spanish: Condado de Washington (Oregón) para niños

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