Expansion Period 1880-1900
The 4,700 HP Superior Engine at Calumet & Hecla

By this time in America, the effects of the 1873 depression were long gone.  Railroads were opening the western frontiers and finding their way into almost every city and village.  And technological advances, like electricity, were increasing the demand for copper every year.
C&H was the largest producer of copper in America, thanks to machinery like the Superior engine (above) and the mines of Houghton County were soon dominating Michigan's copper production.  The mines of Keweenaw County were almost extinct, though some survived into the 20th century.  Here are some interesting companies and their history...

Atlas Mining Company
Centennial
Conglomerate
Laurium
Quincy
Pewabic
Tamarack
Other mining companies...