Oregon Territory in the context of Oregon City, Oregon

James Knox Polk (/poʊk/; November 2, 1795 – June 15, 1849) was the 11th president of the United States, serving from 1845 to 1849. A protégé of Andrew Jackson and a member of the Democratic Party, he was an advocate of Jacksonian democracy and American expansionism. Polk saw Texas join the Union in his first year in office, one of the precipitating causes that soon led the U.S. into the Mexican–American War. The settlement of that war expanded American territory to the Pacific Ocean. During his term, the dispute over the Oregon Territory with the United Kingdom was also resolved, creating the present U.S.-Canadian boundary.

After building a successful law practice in Tennessee, Polk was elected to its state legislature in 1823 and then to the United States House of Representatives in 1825, becoming a strong supporter of Jackson. Following his tenure as chairman of the Ways and Means Committee, he became Speaker of the House in 1835, the only person to serve both as Speaker and U.S. president. Polk left Congress to run for governor of Tennessee, winning in 1839 but losing in 1841 and 1843. He was a dark-horse candidate in the 1844 presidential election as the Democratic Party nominee. Polk entered his party's convention as a potential nominee for vice president but emerged as a compromise to head the ticket when no presidential candidate could gain the necessary two-thirds majority. In the general election, he narrowly defeated Henry Clay of the Whig Party and pledged to serve only one term.

Oregon (/ˈɒrɪɡən, -ɡɒn/ ORR-ih-ghən, -⁠gon) is a 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, while the Snake River delineates much of its eastern boundary with Idaho. The 42° north parallel delineates the southern boundary with California and Nevada. The western boundary is formed by the Pacific Ocean.

Oregon has been home to many indigenous nations for thousands of years. The first European traders, explorers, and settlers began exploring what is now Oregon's Pacific coast in the early to mid-16th century. As early as 1564, the Spanish began sending vessels northeast from the Philippines, riding the Kuroshio Current in a sweeping circular route across the northern part of the Pacific. In 1592, Juan de Fuca undertook detailed mapping and studies of ocean currents in the Pacific Northwest, including the Oregon coast as well as the strait now bearing his name. The Lewis and Clark Expedition traversed Oregon in the early 19th century, and the first permanent European settlements in Oregon were established soon afterward by trappers and fur traders. The United States received joint occupation rights to the region from the United Kingdom through the Treaty of 1818. The Oregon Treaty of 1846 formally brought Oregon under American sovereignty, and the Oregon Territory was created two years later. Oregon was admitted to the United States on February 14, 1859, becoming the 33rd state.

Idaho (/ˈaɪdəhoʊ/ ) is a landlocked state in the Pacific Northwest and Mountain West subregions of the Western United States. It borders Montana and Wyoming to the east, Nevada and Utah to the south, and Washington and Oregon to the west; the state shares a small portion of the Canada–United States border to the north with the Canadian province of British Columbia. Idaho's state capital and largest city is Boise. With an area of 83,569 square miles (216,440 km), Idaho is the 14th-largest state by land area. The state has a population of approximately two million people; it ranks as the 13th-least populous and the seventh-least densely populated of the 50 U.S. states.

For thousands of years, and prior to European colonization, Idaho had been inhabited by natives. In the early 19th century, Idaho was considered part of the Oregon Country, an area which was disputed between the U.S. and the British Empire. Idaho officially became a U.S. territory with the signing of the Oregon Treaty of 1846, but a separate Idaho Territory was not organized until 1863, instead being included for periods in Oregon Territory and Washington Territory. The state was eventually admitted to the Union on July 3, 1890, becoming the 43rd state.

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.

The Pacific Slope describes geographic regions in North American, Central American, and South American countries that are west of the continental divide and slope down to the Pacific Ocean. In North America, the Rocky Mountains mark the eastern border of the Pacific Slope. In Central and South America, the region is much narrower, confined by the Sierra Madre Occidental in Central America, and by the Andes in South America. The phrase is still used today mostly for scientific purposes to refer to regions inhabited by specific species.

It was and is still occasionally used to describe the region in North America during the 19th century and the expansion of the Old West. It includes the states and territories west of the continental divide that runs down the Rocky Mountains in North America. This included the territories and the states that emerged from them, including California, Oregon Territory, Washington Territory, Nevada Territory, Idaho Territory, Colorado Territory, and Utah Territory. The region is drained by the Columbia, Sacramento, San Joaquin and Colorado River systems. In the United States, the Pacific-slope flycatcher takes its name from the region it inhabits.

Jefferson County is a county located in the U.S. state of Washington. As of the 2020 census, the population was 32,977. The county seat and only incorporated city is Port Townsend. The county is named for Thomas Jefferson.

Jefferson County was formed out of Thurston County on December 22, 1852, by the legislature of Oregon Territory, and included the northern 4,854-square-mile (12,571.8 km) portion of the Olympic Peninsula. On April 26, 1854, the legislature of Washington Territory created Clallam County from the northwestern 2,670-square-mile (6,915.3 km) portion of this original area.

The Washington Territory was an organized incorporated territory of the United States that existed from March 2, 1853, until November 11, 1889, when the territory was admitted to the Union as the State of Washington. It was created from the portion of the Oregon Territory north of the lower Columbia River and north of the 46th parallel east of the Columbia. At its largest extent, it also included the entirety of modern Idaho and parts of Montana and Wyoming, before attaining its final boundaries in 1863.

The U.S. state of Washington has 39 counties. The Provisional Government of Oregon established Vancouver and Lewis Counties in 1845 in unorganized Oregon Country, extending from the Columbia River north to 54°40′ north latitude. After the region was organized within the Oregon Territory with the current northern border of 49° north, Vancouver County was renamed Clark, and six more counties were created out of Lewis County before the organization of Washington Territory in 1853; 28 were formed during Washington's territorial period, two of which only existed briefly. The final five were established in the 22 years after Washington was admitted to the Union as the 42nd state in 1889.

Article XI of the Washington State Constitution addresses the organization of counties. New counties must have a population of at least 2,000 and no county can be reduced to a population below 4,000 due to partitioning to create a new county. To alter the area of a county, the state constitution requires a petition of the "majority of the voters" in that area. A number of county partition proposals in the 1990s interpreted this as a majority of people who voted, until a 1998 ruling by the Washington Supreme Court clarified that they would need a majority of registered voters. No changes to counties have been made since the formation of Pend Oreille County in 1911, except when the small area of Cliffdell was moved from Kittitas to Yakima County in 1970.

Oregon pioneer history (1806–1890) is the period in the history of Oregon Country and Oregon Territory, in the present day state of Oregon and Northwestern United States.

It was the era when pioneers and mountain men, primarily of European descent, traveled west across North America to explore and settle the lands west of the Rocky Mountains and north of California. Some also arrived via the Pacific Ocean, traveling by ship either around Cape Horn or by changing ships at Panama. The period begins after the explorations of the lower Columbia River by Robert Gray and George Vancouver in 1792, along with the 1804–1806 Lewis and Clark Expedition to Oregon Country, and runs until circa 1890 when railroads and urban centers created a more settled state.