There are 36 counties in the U.S. State of Oregon. The Oregon Constitution does not explicitly provide for county seats; Article VI, covering the "Administrative Department" of the state of Oregon, simply states that:
|Counties of Oregon|
|Location||State of Oregon|
|Populations||1,451 (Wheeler) – 803,377 (Multnomah)|
|Areas||435 square miles (1,130 km2) (Multnomah) – 10,135 square miles (26,250 km2) (Harney)|
- All county and city officers shall keep their respective offices at such places therein, and perform such duties, as may be prescribed by law.
The Federal Information Processing Standard (FIPS) code, which is used by the United States government to uniquely identify counties, is provided with each entry. The FIPS code for each county links to census data for that county.
||FIPS code||County seat||Est.||Origin||Etymology||Population||Area||Map|
|Baker County||001||Baker City||1862||Eastern portion of Wasco County||Edward Dickinson Baker, a senator from Oregon who was killed at Ball's Bluff, a battle of the American Civil War.||16,847||3,068 sq mi
|Benton County||003||Corvallis||1847||Polk County||Thomas Hart Benton (1782–1858), a U.S. senator who advocated U.S. control over the Oregon Country.||96,017||676 sq mi
|Clackamas County||005||Oregon City||1843||One of the original four districts of the Oregon Country||The Clackamas Indians, a Native American tribe living in the area.||422,537||1,868 sq mi
|Clatsop County||007||Astoria||1844||Northern and western portions of the original Twality District||Clatsop tribe of Native Americans, who lived along the coast of the Pacific Ocean prior to European settlement.||41,810||827 sq mi
|Columbia County||009||Saint Helens||1854||Northern half of Washington County||Columbia River, which forms the county's northern borders.||53,074||657 sq mi
|Coos County||011||Coquille||1853||Western parts of Umpqua and Jackson Counties||The Coos Tribe of Native Americans who lived in the region.||64,999||1,600 sq mi
|Crook County||013||Prineville||1882||Southern part of Wasco County||George Crook (1828–1890), a U.S. Army officer who served in the American Civil War and the Indian Wars.||25,739||2,980 sq mi
|Curry County||015||Gold Beach||1855||Coos County||George Law Curry (1820–1878), a governor of the Oregon Territory.||23,683||1,627 sq mi
|Deschutes County||017||Bend||1916||Southern part of Crook County||"Riviere des Chutes", French for "River of the Falls".||204,801||3,018 sq mi
|Douglas County||019||Roseburg||1852||Portion of Umpqua County which lay east of the Coast Range summit||Stephen A. Douglas (1813–1861), a U.S. Senator who supported Oregon statehood.||111,978||5,037 sq mi
|Gilliam County||021||Condon||1885||Eastern third of Wasco County||Cornelius Gilliam (1798–1848), a pioneer who commanded the forces of the Provisional Government of Oregon after the Whitman massacre.||2,005||1,204 sq mi
|Grant County||023||Canyon City||1864||Parts of old Wasco and old Umatilla counties||Ulysses S. Grant (1822–1885), army officer who served in the Oregon Territory; a Union general in the American Civil War at the time of the county's creation; and subsequently President of the United States (1869–1877).||7,272||4,529 sq mi
|Harney County||025||Burns||1889||Southern two-thirds of Grant County||William S. Harney (1800–1889), a cavalry officer of the period, who was involved in the Pig War.||7,575||10,135 sq mi
|Hood River County||027||Hood River||1908||Northwest portion of Wasco County||The Hood River (a tributary of the Columbia River), which flows through the county.||24,057||522 sq mi
|Jackson County||029||Medford||1852||Southwestern portion of Lane County and unorganized area south of Douglas and Umpqua Counties.||Andrew Jackson||223,734||2,785 sq mi
|Jefferson County||031||Madras||1914||Crook County||Mount Jefferson, located on its western boundary, which was named for Thomas Jefferson.||25,068||1,781 sq mi
|Josephine County||033||Grants Pass||1856||Western half of Jackson County||Virginia "Josephine" Rollins (1834-1912), the first white woman to make this county her home.||88,346||1,640 sq mi
|Klamath County||035||Klamath Falls||1882||Western part of Lake County||The Klamath or Clamitte tribe, which has had a presence in the area for 10,000 years.||70,164||5,945 sq mi
|Lake County||037||Lakeview||1874||Jackson and Wasco Counties||Numerous lakes and hot springs.||8,276||7,940 sq mi
|Lane County||039||Eugene||1851||Southern part of Linn County and the portion of Benton County east of Umpqua County||Gen. Joseph Lane (1801–1881), the first governor of Oregon Territory.||383,189||4,554 sq mi
|Lincoln County||041||Newport||1893||Western portion of Benton County and Polk County||Abraham Lincoln||50,862||980 sq mi
|Linn County||043||Albany||1847||Southern portion of Champoeg (later Marion) County||U.S. Senator Lewis F. Linn (1795–1843) of Missouri, author of the Donation Land Act, which provided free land to settlers in the West.||129,839||2,291 sq mi
|Malheur County||045||Vale||1887||Southern portion of Baker County||Malheur River (formally "Riviere au Malheur" or "Unfortunate River"), named by French trappers whose property and furs were stolen from their river encampment.||31,693||9,888 sq mi
|Marion County||047||Salem||1843||One of the original four districts of the Oregon territory||Francis Marion||347,119||1,185 sq mi
|Morrow County||049||Heppner||1885||Western portion of Umatilla County and a small portion of eastern Wasco County||Jackson L. Morrow, a state representative who advocated for the formation of the county.||12,303||2,033 sq mi
|Multnomah County||051||Portland||1854||Eastern part of Washington and the northern part of Clackamas counties||The Indian village of Multnomah, on Sauvie Island. The word is derived from nematlnomaq, probably meaning downriver. Lewis and Clark made note of the name in 1805, and applied that name to all local Indians.||803,377||435 sq mi
|Polk County||053||Dallas||1845||Yamhill District||James Knox Polk (1795–1849), President of the United States at the time of the county's creation||89,164||741 sq mi
|Sherman County||055||Moro||1889||Northeast corner of Wasco County||William Tecumseh Sherman (1820–1891), American Civil War general, and businessman, educator, and author||1,907||823 sq mi
|Tillamook County||057||Tillamook||1853||Clatsop, Yamhill and Polk Counties||Tillamook (or Killamook) Native American people.||27,748||1,102 sq mi
|Umatilla County||059||Pendleton||1862||Central portion of Wasco County||Sahaptin word, possibly meaning laughing waters.||79,988||3,215 sq mi
|Union County||061||La Grande||1864||Baker County||The town of Union, which had been established two years before and named by its founders for the "Union" of the states during the Civil War.||26,212||2,037 sq mi
|Wallowa County||063||Enterprise||1887||Eastern portion of Union County.||The Nez Perce word wallowa to designate a tripod of poles used to support fish nets. The area was claimed by the Chief Joseph band of the Nez Perce as its hunting and fishing grounds.||7,545||3,145 sq mi
|Wasco County||065||The Dalles||1854||Parts of Clackamas, Lane, Linn and Marion counties||The Wasco (or Wascopam) Native American tribe.||26,726||2,381 sq mi
|Washington County||067||Hillsboro||1843||One of the original four districts of the Oregon Country (as Twality District)||George Washington||600,811||724 sq mi
|Wheeler County||069||Fossil||1899||Grant County, Gilliam County, and Crook County||Henry H. Wheeler (1826-1915), who operated the first mail stage line from The Dalles to Canyon City.||1,451||1,715 sq mi
|Yamhill County||071||McMinnville||1843||One of the original four districts of the Oregon Country||The Yamhelas, members of the Kalapuya Native American family, who lived along the Yamhill River in the western Willamette Valley.||108,239||716 sq mi
- "U.S. Census Bureau QuickFacts: Multnomah County, Oregon". census.gov.
- "Oregon Secretary of State: Constitution of Oregon". sos.oregon.gov.
- "EPA County FIPS Code Listing". EPA. Retrieved April 9, 2007.
- National Association of Counties. "NACo – Find a county". Archived from the original on October 25, 2007. Retrieved April 26, 2007.
- Oregon State Archives. "County Government". Oregon Blue Book. Retrieved February 23, 2008.
- "U.S. Census Bureau QuickFacts: Oregon". U.S. Census Bureau. Retrieved March 31, 2022.