Getting soft ore out of an open pit wasn't much
 like blasting hard ore out of solid rock two
 thousand feet down and hauling it to the surface.
 One steam shovel could mine as much Mesabi ore in
 an hour as five hundred miners could bring up in
 a day from the old deep mines.(21)

 While the end results were the same, open pit

mining was so different from underground operations that,

in effect, the means of obtaining minerals was revolutionized.

 Open pit methods, first employed extensively on

the Mesabi range, accounted for almost half the iron

ore produced domestically by 1909. In 1969 nearly 90

percent of iron ore produced domestically was being

mined by this method.22 Similarly, while less than

one-fourth of copper ore produced domestically in 1919

was produced in open pit mines, by 1969, 88 percent of

all copper ore produced in the United States was taken

from open pits.23

 As a result of the application of new technology

and the introduction of power, output per man-hour and

man-day increased rapidly in both the copper and iron

mining industries during the latter part of the

nineteenth century. By 1889 copper output per man-day


 21Holbrook, Iron Brew, p. 108.

 22Minerals Yearbook, 1969, p. 463.

 23Ibid., p. 572.