THE WASHINGTON COUNTY LAND BRIEF
Land in the
Prairie Terraces setting.
Washington County has 724.3 square miles of land in Oregon. 5 mapped landscape regions meet across Washington County: Prairie Terraces, Valley Foothills, Volcanics, among others.
The Willamette River's floodplains and terraces sit among low hills and scattered buttes. The valley's prairie, oak and riparian landscape differs markedly from the conifer-covered mountains around it.
Regional context: Willamette Valley ↗ · Regional mapping across the county footprint
Where the landscape changes
Washington County intersects 5 mapped regional units. The largest mapped shares are:
- Prairie Terraces36.6%
- Valley Foothills30.5%
- Volcanics17.9%
- Willapa Hills10.9%
- Willamette River and Tributaries Gallery Forest4.1%
Coast Range in Washington County
Pacific-facing coastal mountains support moisture-loving conifers, with marine terraces, dunes and beaches along the ocean edge. Inland slopes and the immediate coast have different vegetation patterns.
Read the regional source ↗Finding your parcel within Washington County
The atlas lists 31 cities, towns, townships, and Census communities associated with Washington County, including Portland, Hillsboro, Beaverton. The list includes overlapping geography types and does not divide the county into exclusive service areas.
Washington County by land and water
The Census records 2.36 square miles of water within Washington County, or 0.3% of its total area. That share is close to Washington County’s 0.3%. This is geographic context; waterfront status and usable land must be checked at the parcel.
For scale, Washington County has 120.8 times the land area of nearby Forest Grove city (5.99 square miles). These areas describe boundaries, not comparable property prices.
The Census boundary meets Clackamas County, Clatsop County, Columbia County, Multnomah County, Tillamook County, Yamhill County within Oregon. A tract near one of these lines should be matched to the county identifier on its own records.

