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

Portland Portland most commonly refers to: *Portland, Oregon, the most populous city in the U.S. state of Oregon *Portland, Maine, the most populous city in the U.S. state of Maine *Isle of Portland, a tied island in the English Channel Portland may also r ...

) 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 metropolitan area. The state's smallest and most populous county, it ...

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

, 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 o ...

, they separate the Tualatin Basin of

Washington County, Oregon Washington County is one of Oregon counties, 36 counties in the U.S. state of Oregon and part of the Portland metropolitan area. The 2020 United States census, 2020 census recorded the population as 600,372, making it the second most populous c ...

, from the

Portland Basin Dukinfield Junction () is the name of the Junction (canal), canal junction where the Peak Forest Canal, the Ashton Canal and the Huddersfield Narrow Canal meet near Ashton-under-Lyne, Greater Manchester, England. The area has been designated by ...

of western Multnomah County and

Clark County Clark County may refer to: *Clark County, Arkansas *Clark County, Idaho *Clark County, Illinois *Clark County, Indiana *Clark County, Kansas *Clark County, Kentucky *Clark County, Missouri *Clark County, Nevada, containing Las Vegas *Clark County, ...

Washington Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A ...

. The highest peak in the range is Dixie Mountain at . Other notable peaks include Cornell Mountain at 1,270 feet (390m),

Council Crest Council Crest Park is a city park in southwest Portland in the U.S. state of Oregon. Amenities include paved and unpaved paths, a dog off-leash area, picnic tables, public art, a view point, and a wedding site that can be reserved. The park, op ...

at , and Pittock Hill, location of the Pittock Mansion. Despite steep slopes, periodic landslides, and multiple

earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...

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 Fore ...

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

History

The hills date from the late

Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...

era, and range up to over . Composed mainly of

basalt Basalt (; ) is an aphanite, 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 planetary surface, surface of a terrestrial ...

, 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 Chinook may refer to: Chinook peoples The name derives from a settlement of Indigenous people in Oregon and Washington State. * Chinookan peoples, several groups of Indigenous people of the Pacific Northwest ** Chinook Indian Nation, an organiza ...

people.

U.S. Route 26 U.S. Highway 26 (US 26) is an east–west United States Numbered Highway that runs from Seaside, Oregon, to Ogallala, Nebraska. When the U.S. Numbered Highway System was first defined, it was limited to Nebraska and Wyoming; by the 1950s, it c ...

(the Sunset Highway) is the principal transportation link through the hills, traveling through the

Vista Ridge Tunnels The Vista Ridge Tunnels are highway tunnels through the Tualatin Mountains ("West Hills") of Portland, Oregon, United States. With their eastern ends located in the Goose Hollow, Portland, Oregon, Goose Hollow neighborhood, the tunnels pass th ...

, 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 Plank (wood), wooden planks or wikt:puncheon#Noun, puncheon logs, as an efficient technology for traversing soft, marshy, or otherwise difficult ground. Plank roads have been built since antiquity, and were comm ...

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 West Side or Westside may refer to: Places Canada * West Side, a neighbourhood of Windsor, Ontario * West Side, a neighbourhood of Vancouver, British Columbia United Kingdom * West Side, Lewis, Outer Hebrides, Scotland * Westside, Birmingham ...

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 lines connecting the Neighborhoods of Portland, Oregon, 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 KLTH (106.7 MHz "The Eagle") is a commercial FM radio station, licensed to Lake Oswego, Oregon, and serving the Portland metropolitan area. It is owned by iHeartMedia, Inc., and airs a classic hits radio format. Specialty programs on KLTH ...

History

Radio broadcasters

See also

References

Further reading