It seemed, in 1862 and 1863, as though every little rivulet in the whole mountain country possessed its treasures to be given up to the first prospector with the hardihood to tickle its soil. Four important districts along the upper course of the Snake, not to mention hundreds of minor ones, lent substance to this appearance. Almost before Idaho could be organized its area of settlement had broadened enough to make its own division in the near future a certainty. East of the Bitter Root Mountains, in the head waters of the Missouri tributaries, came a long series of new booms. When the American Fur Company pushed its little steamer _Chippewa_ up to the vicinity of Fort Benton in 1859, none realized that a new era for the upper Missouri had nearly arrived. For half a century the fur trade had been followed in this region and had dotted the country with tiny forts and palisades, but there had been no immigration, and no reason for any. The Mullan road, which Congress had authorized in 1855, was in course of construction from Fort Benton to Walla Walla, but as yet there were few immigrants to follow the new route. Considerably before the territory of Idaho was created, however, the active prospectors of the Snake Valley had crossed the range and inspected most of the Blackfoot country in the direction of Fort Benton. They had organized for themselves a Missoula County, Washington territory, in July, 1862, an act which may be taken as the beginning of an entirely new movement. Two brothers, James and Granville Stuart, were the leaders in developing new mineral areas east of the main range. After experience in California and several years of life along the trails, they settled down in the Deer Lodge Valley, and began to open up their mines in 1861. They accomplished little this year since the steamboat to Fort Benton, carrying supplies, was burned, and their trip to Walla Walla for shovels and picks took up the rest of the season. But early in 1862 they were hard and successfully at work. Reënforcements, destined for the Salmon River mines farther west, came to them in June; one party from Fort Benton, the other from the Colorado diggings, and both were easily persuaded to stay and join in organizing Missoula County. Bannack City became the centre of their operations. Alder Gulch and Virginia City were, in 1863, a second focus for the mines of eastern Idaho. Their deposits had been found by accident by a prospecting party which was returning to Bannack City after an unsuccessful trip. The party, which had been investigating the Big Horn Mountains, discovered Alder Gulch between the Beaver Head and Madison rivers, early in June. With an accurate knowledge of the mining population, the discoverers organized the mining district and registered their own claims before revealing the location of the new diggings. Then came a stampede from Bannack City which gave to Virginia City a population of 10,000 by 1864.