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. Th ...

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

, 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 Dukinfield Junction () is the name of the 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 Tameside Metropol ...

of western Multnomah County and Clark County,

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

. 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 The Pittock Mansion is a French Renaissance-style château in the West Hills of Portland, Oregon, United States. The mansion was originally built in 1914 as a private home for London-born '' Oregonian'' publisher Henry Pittock and his wife, Georg ...

. 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 Fores ...

. 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 configura ...

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 people.

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

(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 b ...

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 as well as the Northeast and Midwest of the United States in the first half of the 19th century. They were oft ...

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 E ...

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 sections ...

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