The main defence of the last frontier by the Indians ceased with the termination of the Indian wars of the sixties. Here the resistance had most closely resembled a general war with the tribes in close alliance against the invader. With this obstacle overcome, the work left to be done in the conquest of the continent fell into two main classes: terminating Indian resistance by the suppression of sporadic outbreaks in remote byways and letting in the population. The new course of the Indian problem after 1869 led it speedily away from the part it had played in frontier advance until it became merely one of many social or race problems in the United States. It lost its special place as the great illustration of the difficulties of frontier life. But although the new course tended toward chronic peace, there were frequent relapses, here and there, which produced a series of Indian flurries after 1869. Never again do these episodes resemble, however remotely, a general Indian war. Human nature did not change with the adoption of the so-called peace policy. The government had constantly to be on guard against the dishonest agent, while improved facilities in communication increased the squatters' ability to intrude upon valuable lands. The Sioux treaty of 1868, whereby the United States abandoned the Powder River route and erected the great reserve in Dakota, west of the Missouri River, was scarcely dry before rumors of the discovery of gold in the Black Hills turned the eyes of prospectors thither.