The Tualatin Mountains (also known as the West Hills or Southwest Hills of

Portland Portland most commonly refers to: * Portland, Oregon, the largest city in the state of Oregon, in the Pacific Northwest region of the United States * Portland, Maine, the largest city in the state of Maine, in the New England region of the northeas ...

) are a range on the western border of

Multnomah County Multnomah County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the county's population was 815,428. Multnomah County is part of the Portland–Vancouver– Hillsboro, OR–WA Metropolitan Statistical Area. Tho ...

Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idah ...

, United States. A spur of the

Northern Oregon Coast Range The Northern Oregon Coast Range is the northern section of the Oregon Coast Range, in the Pacific Coast Ranges physiographic region, located in the northwest portion of the state of Oregon, United States. This section of the mountain range, part ...

, they separate the Tualatin Basin of

Washington County, Oregon 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 "Wa ...

, from the Portland Basin of western Multnomah County and Clark County, Washington. The highest peak in the range is Dixie Mountain at . Other notable peaks include Cornell Mountain at 1,270 feet (390m), Council Crest at , and Pittock Hill, location of the Pittock Mansion. Despite steep slopes, periodic landslides, and multiple

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

faults, many residences have been built in the Tualatin Mountains, though much of the northern portion is undeveloped land within the

Forest Park A forest park is a park whose main theme is its forest of trees. Forest parks are found both in the mountains and in the urban environment. Examples Chile * Forest Park, Santiago China * Gongqing Forest Park, Shanghai * Mufushan National Fo ...

. The landscape, inside and outside the park, is predominantly forested.

History

The hills date from the late

Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configu ...

era, and range up to over . Composed mainly of

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of a ...

, the mountains were formed by several flows of the Grande Ronde basalt flows that were part of the larger Columbia River basalts.Bishop, Ellen Morris. ''In Search of Ancient Oregon: A Geological and Natural History''. Timber Press, 2003. Human settlement goes back 10,000 years to the area's earliest known residents, the Chinook people. U.S. Route 26 (the Sunset Highway) is the principal transportation link through the hills, traveling through the Vista Ridge Tunnels, Tanner Creek Canyon, and over the crest of Sylvan Hill. This route through the hills connecting the agricultural Tualatin Basin to the navigable

Willamette River The Willamette River ( ) is a major tributary of the Columbia River, accounting for 12 to 15 percent of the Columbia's flow. The Willamette's main stem is long, lying entirely in northwestern Oregon in the United States. Flowing northward ...

was developed as a

plank road A plank road is a road composed of wooden planks or puncheon logs. Plank roads were commonly found in the Canadian province of Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geog ...

in the 19th century. The Great Plank Road (Canyon/Jefferson Road) was a major factor in the early growth of the city of Portland. Since 1998, the west side

MAX Light Rail The Metropolitan Area Express (MAX) is a light rail system serving the Portland metropolitan area in the U.S. state of Oregon. Owned and operated by TriMet, it consists of five color-designated lines that altogether connect the six sectio ...

has run roughly parallel to US 26 through the hills, including a section tunneled deep underground.

Radio broadcasters

The Tualatin Mountains are home to the transmitter for iHeartMedia's KLTH.

History

Radio broadcasters

See also

References

Further reading