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 "Washington County" in the United States. Hillsboro is the county seat and largest city, while other major cities include Beaverton, Tigard, Cornelius, Banks, Gaston, Sherwood, North Plains, and Forest Grove, the county's oldest city. Originally named Twality when created in 1843, the Oregon Territorial Legislature renamed it for the nation's first president in 1849 and included the entire northwest corner of Oregon before new counties were created in 1854. The Tualatin River and its drainage basin lie almost entirely within the county, which shares its boundaries with the Tualatin Valley. It is bordered on the west and north by the Northern Oregon Coast Range, on the south by the Chehalem Mountains, and on the north and east by the Tualatin Mountains, or West Hills.
The Pacific Coast Ranges are the series of mountain ranges that stretch along the West Coast of North America from Alaska south to Northern and Central Mexico. Although they are commonly thought to be the westernmost mountain range of the continental United States and Canada, the geologically distinct Insular Mountains of Vancouver Island lie further west.
The Warner Mountains are an 85-mile (137 km)-long mountain range running north–south through northeastern California and extending into southern Oregon in the United States. The range lies within the northwestern corner of the Basin and Range Province, extending from the northeastern corner of Lassen County, California, through eastern Modoc County, California, and northward into Lake County, Oregon.
The Calapooya Mountains are a mountain range in Lane and Douglas counties of southwestern Oregon in the United States. The range runs for approximately 60 miles (97 km) west from the Cascade Range between Eugene on the north and Roseburg on the south.
The Tualatin Valley is a farming and suburban region southwest of Portland, Oregon. The valley is formed by the meandering Tualatin River, a tributary of the Willamette River at the northwest corner of the Willamette Valley, east of the Northern Oregon Coast Range. Most of the valley is located within Washington County, separated from Portland by the Tualatin Mountains. Communities in the Tualatin Valley include Banks, Forest Grove, Cornelius, Hillsboro, Aloha, Beaverton, Sherwood, Tigard, and Tualatin.
The Verdugo Mountains, also known as the Verdugo Hills or simply The Verdugos, are a small, rugged mountain range of the Transverse Ranges system in Los Angeles County, California. Located just south of the western San Gabriel Mountains, the Verdugo Mountains region incorporates the cities of Glendale, Pasadena, and La Cañada Flintridge; the unincorporated communities of Altadena and La Crescenta-Montrose; as well as the City of Los Angeles neighborhood of Sunland-Tujunga.
The Tualatin Mountains are a range on the western border of Multnomah County, Oregon, United States. A spur of the Northern Oregon Coast Range, they separate the Tualatin Basin of Washington County, Oregon, from the Portland Basin of western Multnomah County and Clark County, Washington.
Diamond Peak is a volcano in Klamath and Lane counties of central Oregon in the United States. It is a shield volcano, though it might also be considered a modest stratocone. Diamond Peak forms part of the Cascade Volcanic Arc, a segment of the Cascade Range in western North America extending from southern British Columbia through Oregon to Northern California. Reaching an elevation of 8,748 feet (2,666 m), the mountain is located near Willamette Pass in the Diamond Peak Wilderness within the Deschutes and Willamette national forests. Surrounded by coniferous forest and visible in the skyline from foothills near Eugene, Diamond Peak offers a few climbing routes and can be scrambled. Diamond Peak is one of Oregon's Matterhorns.
The Mount Thielsen Wilderness is a wilderness area located on and around Mount Thielsen in the southern Cascade Range of Oregon in the United States. It is located within the Deschutes, Umpqua, and Fremont–Winema national forests. It was established by the United States Congress in 1984 and comprises 55,100 acres (22,300 ha).
Hogg Rock is a tuya volcano and lava dome in the Cascade Range of northern Oregon, located close to Santiam Pass. Produced by magma with an intermediate andesite composition, it has steep slopes and thick glassy margins. Hogg Rock exhibits normal magnetic polarity and is probably about 80,000 years old.
The Middle Fork Willamette River is one of several forks that unite to form the Willamette River in the western part of the U.S. state of Oregon. It is approximately 115 miles (185 km) long, draining an area of the Cascade Range southeast of Eugene, which is at the southern end of the Willamette Valley.
The Waldo Hills are a range of hills in the Willamette Valley of Oregon, United States. Encompassing an area of around 50 square miles (130 km2), the hills are located east of Salem. The hills are named after pioneer Daniel Waldo.
The Coast Range ecoregion is a Level III ecoregion designated by the Environmental Protection Agency (EPA) in the U.S. states of Washington, Oregon, and California. It stretches along the Pacific Coast from the tip of the Olympic Peninsula in the north to the San Francisco Bay in the south, including Grays Harbor, Willapa Bay, and the Long Beach Peninsula in Washington, the entire length of the Oregon Coast, and the Northern California Coast. Named for the Coast Range mountains, it encompasses the lower elevations of the Olympic Mountains, the Oregon Coast Range, the Californian North Coast Ranges, and surrounding lowlands.
The Northern Basin and Range ecoregion is a Level III ecoregion designated by the United States Environmental Protection Agency (EPA) in the U.S. states of Oregon, Idaho, Nevada, Utah, and California. It contains dissected lava plains, rolling hills, alluvial fans, valleys, and scattered mountain ranges in the northern part of the Great Basin. Although arid, the ecoregion is higher and cooler than the Snake River Plain to the north and has more available moisture and a cooler climate than the Central Basin and Range to the south. Its southern boundary is determined by the highest shoreline of Pleistocene Lake Bonneville, which once inundated the Central Basin and Range. The western part of the region is internally drained; its eastern stream network drains to the Snake River system.
The Trout Creek Mountains are a remote, semi-arid Great Basin mountain range mostly in southeastern Oregon and partially in northern Nevada in the United States. The range's highest point is Orevada View Benchmark, 8,506 feet (2,593 m) above sea level, in Nevada. Disaster Peak, elevation 7,781 feet (2,372 m), is another prominent summit in the Nevada portion of the mountains.
Hager Mountain is a volcanic peak in Oregon in the northwest corner of the Basin and Range Province in the United States. The mountain is located south of the small unincorporated community of Silver Lake in south-central Oregon, and it is in the Fremont–Winema National Forest. On the summit, there is a fire lookout operated during the summer and fall by the United States Forest Service. There are several hiking trails that lead to the lookout station.
The Cline Buttes are mountains with volcanic origins that form three dome-shaped peaks located in Deschutes County in central Oregon. They are some of the eastern foothills of the Cascade Range. Situated on land administered by the Bureau of Land Management, the buttes are flanked on the east and west sides by two separate sections of the Eagle Crest Resort. On the highest summit, there is a Federal Aviation Administration site with an aircraft navigation beacon. The mountains have several hiking trails as well as a number of popular mountain bike routes.
