Idaho County existed prior to the Idaho Territory, it was formed in 1862.
County of Idaho
At a regular term of the Hon. District Court of Idaho County, Washington Territory began and held in Florence City in said County on Monday the 22nd day of September A.D. 1862.
As cited in Pioneer Days of Idaho County Volume One, quoting Idaho County, "Records of the District Court, Book 1" (1862-1864).
On March 4, 1863, President Abraham Lincoln signed into law the act that formed the organization of the Territory of Idaho.
Idaho County is the largest County in Idaho. It covers 8,503 square miles, and has 6,925 square miles of National Forest land within the county. (wikipedia)
The area now comprising Idaho County was part of Oregon Territory from 1848 to 1859. With Oregon statehood, it became a part of Washington Territory, and, in 1863, of Idaho Territory. A law in 1875 forced some changes in regards of Idaho County boundaries. Therefore in amendment of that law new boundaries were defined to as they are to this day.
The first settlement in the new county was by gold seekers from Pierce, Idaho, who in 1861 followed the Nez Perce Trail into Elk City Basin, hopeful of finding gravel deposits that would contain gold. The hopes of miners were realized and Elk City became the pioneer settlement of the upper Clearwater county. No town existed until the following year when a local government was established.
The gold seekers trek had begun. News of discoveries in Florence reached the ears of prospectors everywhere. Thousands of men left good gravel deposits for the better promise of gold in the Idaho mountain area of Florence. By the fall of 1862 a town of tents, lean-tos and brush houses had developed into a boom town. Florence became the first county seat town.
By 1875 Mount Idaho was developing into a prosperous town. Built largely as a stop for traffic to the gold fields, it seemed destined to be a more permanent settlement than the boom towns. It won a special election in 1875 for county seat. Mining was spreading to other areas: Orogrande, Dixie, Newsome, Salmon River, Golden, Marshall Lake, Burgdorf and others. Seventeen mining districts existed at that time, according to the Bicentennial Edition of the Idaho County Free Press published in 1976.
Mining activities had slowed down before World War II and the war saw the close of the remaining operations. In years since, several have tried to reopen, but most of today's mining is done with the use of small suction-type dredges that one sees operating along streams.
While the early mining towns were drawing in gold seekers, a new kind of traffic was developing. The Pre-Emption Act of 1841 allowed any American not already owning land to buy 160 acres in the public domain and pay later $ 1.25 per acre. The Homestead act of 1862 supplemented the Pre-emption Act by offering a settler 160 acres of public land for a nominal fee after five years of residence. Stages and wagons lumbered across the Prairie with passengers including families looking to settle on this land, and with entrepreneurs who knew that hotels, livery barns, saloons, blacksmith shops, stores, real estate firms and other businesses would be needed and would provide a profitable living.
While land was available in some areas, land on the Nez Perce Reservation was not open to the settlers until the government concluded a treaty with the Nez Perce Tribe ceding a part of their land to the Federal Government. The opening up of the land gave rise to the growth of agriculture. Many who had come into the State to search for gold remained to take up land, finding their gold in the rich soil and favorable climatic conditions. By 1864 ranches were scattered over the Prairie and along the rivers.
In 1905 at Portland and again in 1909 at Seattle the Idaho County exhibit of grains and grasses won the Gold Medal in competition with several other states. Stock raising began almost simultaneously with the tilling of the soil. Mountains, valleys, river breaks and high plateaus afforded fine grazing land. Cattle, horses, sheep and swine were raised. To breed better horses the pioneers shipped sires from the East.
Idaho County did not escape the wars on ranges between the sheep men and the cattlemen in the early 1900's. The Forest Service stepped in to help control the range. The first passenger train whistled into Grangeville on the Camas Prairie Railroad in 1908 and the present State Cattle Association was organized in the 1920's. Idaho County organized its Association in 1958. Hereford and Aberdeen-Angus eventually became the main breeds of beef cattle.
Following the War, the growth of Grangeville brought another change in county seat. An election gave it to the fast growing town where it has remained 87 years. By 1937 a North-South highway from Bonners Ferry to Boise was completed and all except two small stretches were oiled.
The timber industry developed as an economic asset to the County. In the 1940's this industry began to develop on a full scale. While sawmills, mostly privately owned, were built earlier to produce lumber chiefly for home building, it was the huge demand for timber after World War II that made timber production a leading industry. "Potlatch Forest Inc. began cutting on the first major site on the Forest in 1944 in the Meadow Creek-Cougar Creek area. Within two years 75 million board feet had been taken out of the area.
While mining as an economic asset to the county was short lived, it gave the county its economic beginning and contributed sporadically to the economy throughout its developing years. Forestry and the timber industry, farming and ranching remain the lifeblood of the county, invigorated in recent years by the growth of tourism as a lucrative industry.
Information borrowed from: Idaho County Voices, From The Pioneers To The Present, Pioneer Days in Idaho County Volume 1 by Alfreda Elsensohn.