100 years ago, steam power was ubiquitous. Boilers were the primary means of creating steam, for mechanical power -- steam engines, steam hoists, steam power of all kinds. The Copper Country was home to some of the largest steam engines in the world (and still is, at the Quincy Mine).
Nowadays, of course, boilers are rather rare. During the world wars, most of the old metal boilers were scrapped. Occasionally it's possible to find an old one, lying out and ruined.
Inexplicably, this one survived, in place, still attached to its water feed and vents -- but totally exposed to the elements, too. This was apparently in the old dry house at the Delaware mine. Perhaps the scrappers missed it.