Oregon Territory, created in 1848, originally included all of the land that now makes up the states of Oregon, Washington, and Idaho, as well as the western portion of Montana and the northwestern portion of Wyoming. The Legislative Assembly of Oregon Territory created the basic aspects of governance for the entire territory, including what became the State of Idaho. When Congress created Washington Territory on March 2, 1853, out of a portion of Oregon Territory, the Panhandle of Idaho (and a portion of western Montana) were included as part of the new Washington Territory, while the rest of the future state of Idaho remained in Oregon Territory. Oregon became a state in 1859 when it was admitted into the Union with the same boundaries that it currently has. The eastern parts of what had been Oregon Territory were transferred to Washington Territory, which thereby contained all of the future state of Idaho (and western portions of the future Montana and Wyoming).Governing Idaho from Olympia
During the period that Idaho was part of Washington Territory, the Legislative Assembly of Washington Territory in Olympia enacted legislation expanding some of the aspects of current local government in Idaho. General legislation expanded the details of county government, the basic unit of government in the territory, as well as providing more details for school districts and road districts that were created by and controlled by counties. Special legislation was enacted creating the cities of Boise and Lewiston. Each of those special laws adopted a charter for the city, described the city's boundaries, provided for its system of government, and detailed its powers. The Territorial Assembly of Washington Territory also created counties in what became Idaho, including Idaho County. This was the initial official use of the name "Idaho."
Mining brought the earliest settlers to the future state of Idaho. Gold was first discovered in what became Idaho in the winter of 1860, on the Clearwater branch of the Snake River, located north and east of the future city of Lewiston in the Idaho Panhandle. However, opposition by the Nez Perce Indians prevented mine development until the next year, after a treaty was signed. By the winter of 1861, there were 1,000 miners in the Oro Fino Mining District on the Clearwater, wrote historian Hubert Howe Bancroft,
"with immigration coming in rapidly from California. As the spring advanced the excitement increased, and a line of steamers was put upon the Columbia to accommodate the thousands that rushed impetuously to this richest of all the gold-fields yet discovered north of the Columbia" (Bancroft, 236).
The route to the Clearwater goldfields went from Walla Walla to the confluence of the Clearwater and Snake rivers, where Lewiston, named for explorer Meriwether Lewis (1774-1809), was founded. By the summer of 1861, more than 5,000 men were in the area, and the city of Oro Fino was founded on the Clearwater River. Prospectors were also looking for gold in nearby regions. Finds were made on the South fork of the Clearwater, and the town of Elk Creek was formed. Another party went into the Salmon River basin where gold was discovered in September 1861, causing a new rush of prospectors into the area.
"The excitement which hurried men to the Salmon River mines was intense. Nor was it without justification; for every report from there confirmed and strengthened the accounts given by the first explorers ... . The weight of evidence was to the effect that these mines excelled in richness the placer mines of California in their best days" (Bancroft, 237, 247, 259).
Gold discoveries in the Boise River basin in 1862 attracted even more prospectors, but it was the influx of miners into northern Idaho that had the biggest political impact. Miners in the Oro Fino district organized Nez Perce County in 1862, along with Idaho County, and Washington Territory was reorganized to give the region a federal judge. In territorial elections, more votes were cast in the area from Walla Walla east than anywhere west of the Cascades. "Politically, the effect of the Clearwater gold discoveries was remarkable," wrote Bancroft. The Legislative Assembly of the Territory of Washington was "much embarrassed by the situation," since it was overwhelmed with business west of the Cascades, and the new population in the "great extent of territory" to the east required attention. "In short, eastern Washington had outgrown the Puget Sound region, and was demanding a separate government" (Bancroft, 249, 250, 262).
By 1863, the Washington Legislative Assembly became concerned that the territorial capital in Olympia might be shifted east. With the assistance of political forces from Lewiston, the rapidly growing mining country was removed from Washington Territory to become part of a new Idaho Territory, with its first capital at Lewiston. On March 3, 1863, Congress enacted an Organic Act creating Idaho Territory. The act specified that Idaho Territory included "all that portion of Washington lying east of Oregon and the 117th meridian of west longitude," thereby reducing Washington Territory to the familiar boundaries that the state of Washington still retains.
The newly created Idaho Territory also initially included areas removed from the western portions of Dakota Territory and Nebraska Territory, so that Idaho Territory then encompassed all of the land now included in the states of Idaho and Montana, as well as much of the state of Wyoming. Those boundaries lasted little more than a year. In 1864, the same year that the territorial capital was moved from Lewiston to Boise City, the area that is now the state of Montana became Montana Territory and most of what is now the state of Wyoming was transferred to Dakota Territory. Idaho attained its present boundaries in 1868 when Wyoming Territory was established. Idaho became a state in 1890, one year after Washington.