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 The effects of changing conditions were pervasive.

 Agricultural and manufacturing output increased sub-

 stantially as new techniques and new machines were

 employed to convert rich and abundant resources into

 man-made wealth with unprecedented speed. Metals in the

 ground were converted into metals in use in machines and

 structures. First the railroad, then buildings and

 machines, and finally consumer goods absorbed iron and

 copper at a progressively more rapid rate; and the mining

 sector was responsive to the new demands.

 For the most part, enough metals were available

 to meet increased demands from domestic sources. Vast

 quantities of iron and copper were found shortly before

 and after 1860, and during the century that followed,

 new methods of mining and refining insured a supply of

 new metal adequate to the needs of a burgeoning economy;

 but no large new domestic deposits were located after

 1920, certainly none to compare with the iron deposits

 of the Mesabi or the copper deposits of Michigan,

 Montana, or Arizona. By the 1950s, large quantities of

 iron and copper were being imported into the United

 States, and still demands for new metal products grew

 larger, and the need for new metal supplies increased

unabated. Phenomenal expansions of material wealth had

come to be expected--even demanded. An abundance of

wealth seemed not enough.