Gold is found chiefly in placers, and in colonial times the output was large, but the deposits were long ago exhausted and the industry is now comparatively unimportant.
Rich gold placers had already been discovered, and in 1875 the Sioux Indians within whose territory the hills had until then been included, were removed, and the lands were open to white settlers.
The Atlin and White Horse regions in northern British Columbia and southern Yukon have attracted much attention, and the Klondike placers still farther north have furnished many millions of dollars' worth of gold.
These were the richest " placers," but in them the gold was very unequally distributed.
The second half of the 19th century witnessed several great finds; first, of gold placers on the lower Gila and Colorado (1858-1869); later, of lodes at Tombstone, which flourished from 1879-1886, then decayed, but in 1905 had again become the centre of important mining interests; and still later the development of copper mines at Jerome and around Bisbee.