Another mining district, in Last Chance Gulch, gave rise in 1864 to Helena, the last of the great boom towns of this period. Its situation as well as its resources aided in the growth of Helena, which lay a little west of the Madison fork of the Missouri, and in the direct line from Bannack and Virginia City to Fort Benton. Only 142 miles of easy staging above the head of Missouri River navigation, it was a natural post on the main line of travel to the northwest fields. The excitement over Bannack and Virginia and Helena overlapped in years the period of similar boom in Idaho. It had begun even before Idaho had been created. When this was once organized, the same inconveniences which had justified it, justified as well its division to provide home rule for the miners east of the Bitter Root range. An act of 1864 created Montana territory with the boundaries which the state possesses to-day, while that part of Idaho south of Montana, now Wyoming, was temporarily reattached to Dakota. Idaho assumed its present form. The simultaneous development in all portions of the great West of rich mining camps did much to attract public attention as well as population. In 1863 nearly all of the camps were flourishing. The mountains were occupied for the whole distance from Mexico to Canada, while the trails were crowded with emigrants hunting for fortune. The old trails bore much of the burden of migration as usual, but new spurs were opened to meet new needs. In the north, the Mullan road had made easy travel from Fort Benton to Walla Walla, and had been completed since 1862. Congress authorized in 1864 a new road from eastern Nebraska, which should run north of the Platte trail, and the war department had sent out personally conducted parties of emigrants from the vicinity of St. Paul. The Idaho and Montana mines were accessible from Fort Hall, the former by the old emigrant road, the latter by a new northeast road to Virginia City. The Carson mines were on the main line of the California road. The Arizona fields were commonly reached from California, by way of Fort Yuma.