The term 1 is not limited to underground operations, but includes also surface excavations, as in placer mining and open-air workings of coal and ore deposits by methods similar to quarrying, and boring operations for oil, natural gas or brine.
Helena was established as a placer mining camp in 1864 upon the discovery of gold in Last Chance Gulch.
Quartz-mining has since very largely taken the place of placer-mining, but the two principal gold-producing districts are still that traversed by the Blue Mountains in the northeastern quarter and that drained by the Rogue river in the southwestern corner, a continuation of the California field.
