Willamette Valley in the context of Eugene, Oregon

The Oregon Trail was a 2,170-mile (3,490 km) east–west, large-wheeled wagon route and emigrant trail in North America that connected the Missouri River to valleys in Oregon Territory. The eastern part of the Oregon Trail crossed what is now the states of Kansas, Nebraska, and Wyoming. The western half crossed the current states of Idaho and Oregon.

The Oregon Trail was laid by fur traders and trappers from about 1811 to 1840 and was initially only passable on foot or horseback. By 1836, when the first migrant wagon train was organized in Independence, Missouri, a wagon trail had been cleared to Fort Hall, Idaho. Wagon trails were cleared increasingly farther west and eventually reached the Willamette Valley in Oregon, at which point what came to be called the Oregon Trail was complete. Further improvements in the form of bridges, cutoffs, ferries, and roads made the trip faster and safer. From starting points in Iowa, Missouri, or Nebraska Territory, the routes converged along the lower Platte River Valley near Fort Kearny, Nebraska Territory. They led to fertile farmlands west of the Rocky Mountains.

Eastern Oregon is a region of the U.S. state of Oregon. It is not an officially recognized geographic entity; thus, the boundaries of the region vary according to context. It is sometimes understood to include only the eight easternmost counties in the state; in other contexts, it includes the entire area east of the Cascade Range. Cities in the basic eight-county definition include Baker City, Burns, Hermiston, Pendleton, Boardman, John Day, La Grande, and Ontario. Umatilla County is home to the largest population base in Eastern Oregon, accounting for 42% of the region's residents — more than twice that of the region’s second most populous, Malheur County. Hermiston, located in Umatilla County, is the largest city in the region, accounting for 10% of the population. Major industries include transportation/warehousing, timber, agriculture and tourism. The main transportation corridors are I-84, U.S. Route 395, U.S. Route 97, U.S. Route 26, U.S. Route 30, and U.S. Route 20.

Compared to that of the western part of the state, the climate of Eastern Oregon has a drier continental climate, with much greater seasonal variations in temperature. Unlike the Willamette Valley, Eastern Oregon receives a significant amount of snow in the winter. Some areas receive fewer than 10 inches (250 mm) of rain yearly, classifying them as deserts. This desert climate is in part due to a rain shadow effect caused by the Cascade Range. Pine and juniper forests cover 35% of Eastern Oregon, much in the mountains that include the Blue Mountains, Strawberry Mountains, Wallowa Mountains, Trout Creek Mountains, Ochoco Mountains, and Steens Mountain. Volcanic basalt flows from the Columbia River Basalt Group covered large sections of Eastern Oregon 6 to 17 million years ago. Other landforms include the Alvord Desert, Owyhee Desert, Warner Valley, Deschutes River, Owyhee River, Grande Ronde River, Joseph Canyon, The Honeycombs, and Malheur Butte.

McMinnville is the county seat of and the most populous city in Yamhill County, Oregon, United States, at the base of the Oregon Coast Range. As of the 2020 census, the city had a population of 34,319.

McMinnville is located in the Willamette Valley at the confluence of the North and South forks of the Yamhill River. The city's economy has both industry and service businesses as well as the Evergreen Aviation & Space Museum, home of Howard Hughes's famed Spruce Goose flying boat. Linfield University provides higher education.

Salem (/ˈseɪləm/ SAY-ləm) is the capital city of the U.S. state of Oregon, and the county seat of Marion County. It is located in the center of the Willamette Valley alongside the Willamette River, which runs north through the city. The river forms the boundary between Marion and Polk counties, and the city neighborhood of West Salem is in Polk County.

The population was 175,535 at the 2020 census, and was estimated to be 180,406 in 2024, making it the second-most populous city in the state after Portland and before Eugene.

Clackamas County (/ˈklækəməs/ CLAK-ə-məss) is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 421,401, making it Oregon's third-most populous county. Its county seat is Oregon City. The county was named after the native people living in the area at the time of the coming of Europeans, the Clackamas people, who are part of the Chinookan peoples.

Clackamas County is part of the Portland-Vancouver-Hillsboro, OR-WA Metropolitan Statistical Area. It is in the Willamette Valley.

The Willamette River (/wɪˈlæmɪt/ wil-AM-it) 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 187 miles (301 km) long, lying entirely in northwestern Oregon in the United States. Flowing northward between the Oregon Coast Range and the Cascade Range, the river and its tributaries form the Willamette Valley, a basin that contains two-thirds of Oregon's population, including the state capital, Salem, and the state's largest city, Portland, which surrounds the Willamette's mouth at the Columbia.

Originally created by plate tectonics about 35 million years ago and subsequently altered by volcanism and erosion, the river's drainage basin was significantly modified by the Missoula Floods at the end of the most recent ice age. Humans began living in the watershed over 10,000 years ago. There were once many tribal villages along the lower river and in the area around its mouth on the Columbia. Indigenous peoples lived throughout the upper reaches of the basin as well.

Gresham (/ˈɡrɛʃəm/ GRESH-əm) is a city in the Willamette Valley, Located in Multnomah County in the U.S. state of Oregon, bordered by Portland to the northwest and partially in the southwest. It was first settled in the early 1850s by the Powell brothers. It remained unincorporated until 1905; it was named after Walter Quintin Gresham, an American Civil War general and United States Secretary of State.

The early economy of the city was primarily supported by agriculture, and by the mid-20th century, the city saw a population boom, increasing from 4,000 residents to more than 10,000 between 1960 and 1970. The population was 114,247 at the 2020 census, making it the second most populous city in the county and the fourth-most populous city in Oregon. Gresham is an economic center for eastern Multnomah County.

The Organic Laws of Oregon were two sets of legislation passed in the 1840s by a group of primarily American settlers based in the Willamette Valley. These laws were drafted after the Champoeg Meetings and created the structure of a government in the Oregon Country. At the last Champoeg Meeting in May 1843, the majority voted to create what became the Provisional Government of Oregon. Laws were drafted by the committee and accepted by a popular vote in July. These laws were reformed by a second version in 1845.

The Organic Laws were based on the laws of Iowa Territory and compartmentalized the government into three branches consisting of an executive branch, a legislative branch, and a judiciary. Once the Oregon Territory was formed in 1848, the territorial government took control of the laws and invalidated only one provision of the Organic Laws. On February 14, 1859, Oregon became a state and the Oregon Constitution became the legal framework for the state.