Artwork by Sean McKnight
Although the famous Lewis & Clark expedition wintered in Oregon in late 1805 and early 1806, the first permanent Euro-American settlement in what is now the State of Oregon was Fort Astoria, established in 1811 by John Jacob Astor's Pacific Fur Company. During the War of 1812, the British overtook the settlement and renamed it Fort George. During the peace negotiations, Britain tried to get the United States to drop all claims to the region, but John Jay, who led the American delegation at the Ghent negotiations, refused, ultimately agreeing to other territorial concessions as part of a deal to keep American claims on Oregon (though at the time, the exact boundary would remain in dispute). In 1818, the U.S. formally retook possession of Fort Astoria.
The following decade saw a steady uptick in settlers arriving in "Oregon Country," many of whom were trying to escape the economic uncertainties of the post-war era. Astoria boomed as a "major" port (relatively speaking, it only numbered around 2,000 people by 1825), and settlers began to follow the Columbia River upstream and further up the Willamette River into the fertile Willamette Valley. The British were also eager to settle this area, giving land grants to encourage settlers from British North America to head west as well, some overland and others taking the perilous sea journey. As such, American settlements mostly remained south of the Columbia River - though individual homesteaders did start new lives in the north, with some joining the settlements of Tahoma and Pugetburgh, which today are the two largest cities in the Canadian province of Columbia.
The steady trickle of Euro-American settlers began to grow during the 1830s, with thousands following the Oregon Trail each year, departing from St. Louis, Missouri, up to Fort Calhoun in Platte Territory, then heading northwest across the unsettled West. The Willamette Valley, in particular, was sold to would-be migrants back East as a veritable Garden of Eden, and many people caught the "Oregon Fever" to try and claim their own piece of paradise. Congress passed the Oregon Homestead Act in 1840 to try and encourage still more people to head west, hoping to push the British further north. Still, most Americans remained south of the Columbia. New Boston was settled in 1842, Corvallis in 1844, and McKenzie in 1848, though none of these settlements - except for New Boston - rivaled Astoria in size, with nearly 8,000 people.
Following the Second Mexican War, the Boston Accords of 1848 formally divided the Oregon Country, with the land north of the Columbia remaining in British hands, leading to the formal creation of the Territory of Oregon, with Astoria named the capital. This new territory stretched from the Pacific Coast inland to the Continental Divide. However, the territory remained sparsely populated outside the Willamette Valley, with small settler outposts along the Oregon Trail being the only sign of "civilization." The two largest settlements farther east were Adamston (at the confluence of the Snake and Columbia Rivers) and Snake Falls (present-day Lewis). Both of these towns depended on the Snake River for their existence, remained rough frontier settlements for decades, and were very much only theoretically under the Astoria government's purview. Following the conventions of the 1820 Missouri Compromise, Oregon Territory was declared "free soil." However, there are historical reports of individual slaves being held on farms in the territory at this time, and the settlers were generally hostile to having those of African descent, slave or free, in their midst.
Statehood first began to be seriously discussed in the early 1850s, and there was a failed attempt to organize a constitutional convention in 1853. This failed for two reasons. First, it lacked support from Franklin, where the powers that be did not see a viable slave state to pair up with Oregon. Second, the organizers found too few interested participants outside the Willamette Valley - people in Snake Falls and Adamston were not interested in being a part of a state ran from Astoria or the Willamette Valley. The issue would then be sidelined following President Lee's assassination in 1856 and the subsequent outbreak of war.
During the War Between the States, the Oregon Territorial Legislature, like all the other western territorial governments, remained officially loyal to the Hawthorne Government. In practice, however, Oregon remained neutral, with the legislature refusing to call up volunteers. Some private units were organized, however. These included the New Boston Irregulars, which fought for the Union, and the "Mighty McKenzieites," which fought for the Free States. Most settlers in the Oregon Territory, however, felt that the conflict was an "Eastern Problem" and hoped the conflict would end soon.
When the war finally ended in 1860, talk of statehood quickly took off again. This time, however, the organizers hoped to follow the Arkansas/Jefferson solution. They proposed that most of Oregon Territory east of the Cascades be broken off to form a separate jurisdiction, and the western, Pacific-facing counties organize as the new "State of Oregon." This found plenty of support locally and in Congress, and by the summer of 1862, statehood was made official, with Acting President Hugo Brandt signing the Oregon Enabling Act on July 23rd, 1862, making Oregon the 32nd state in the Union.